Update to sagemath 8.4.

Also:
- Build for python 3 instead of python 2 due to upcoming python 2 removal.
- Add -python3 and -escape patches to fix problems with python 3.
- Drop -nofstring patch, only needed for python 2.
- Drop upstreamed -eclib patch.
- Switch from atlas to openblas and rename -atlas patch to -openblas.
- Add -buildroot patch and only build cython interfaces once.

sagemath-escape.patch

@@ -0,0 +1,108 @@
+--- build/pkgs/sagenb/src/sagenb/misc/sphinxify.py.orig	2018-10-25 14:14:33.031253545 -0600
++++ build/pkgs/sagenb/src/sagenb/misc/sphinxify.py	2018-10-25 15:33:56.358876835 -0600
+@@ -133,7 +133,7 @@ def sphinxify(docstring, format='html'):
+         #    "/media/...path.../blah.png"
+         # to
+         #    "/doc/static/reference/media/...path.../blah.png"
+-        output = re.sub("""src=['"](/?\.\.)*/?media/([^"']*)['"]""",
++        output = re.sub("""src=['"](/?\\.\\.)*/?media/([^"']*)['"]""",
+                           'src="/doc/static/reference/media/\\2"',
+                           output)
+         # Remove spurious \(, \), \[, \].
+--- build/pkgs/sagenb/src/sagenb/misc/support.py.orig	2018-10-25 13:30:02.499892169 -0600
++++ build/pkgs/sagenb/src/sagenb/misc/support.py	2018-10-25 14:14:33.032253542 -0600
+@@ -550,7 +550,7 @@ try:
+             return args[0].__getattribute__(str(self))(*args[1:], **kwds)
+ 
+     def automatic_name_eval(s, globals, max_names=10000):
+-        """
++        r"""
+         Exec the string ``s`` in the scope of the ``globals``
+         dictionary, and if any :exc:`NameError`\ s are raised, try to
+         fix them by defining the variable that caused the error to be
+--- build/pkgs/sagenb/src/sagenb/notebook/cell.py.orig	2018-10-25 13:30:55.707737342 -0600
++++ build/pkgs/sagenb/src/sagenb/notebook/cell.py	2018-10-25 14:14:33.032253542 -0600
+@@ -441,7 +441,7 @@ class Cell_generic(object):
+         return isinstance(self, Cell)
+ 
+     def is_auto_cell(self):
+-        """
++        r"""
+         Returns whether this is an automatically evaluated generic
+         cell.  This is always false for :class:`Cell_generic`\ s and
+         :class:`TextCell`\ s.
+@@ -647,7 +647,7 @@ class TextCell(Cell_generic):
+         return self._text
+ 
+     def set_cell_output_type(self, typ='wrap'):
+-        """
++        r"""
+         Sets this text cell's output type.  This does nothing for
+         :class:`TextCell`\ s.
+ 
+@@ -1320,8 +1320,8 @@ class Cell(Cell_generic):
+         if len(s) == 0:
+             return False
+         s = s[0]
+-        return bool(re.search('(?<!\w)interact\s*\(.*\).*', s) or
+-                    re.search('\s*@\s*interact', s))
++        return bool(re.search(r'(?<!\w)interact\s*\(.*\).*', s) or
++                    re.search(r'\s*@\s*interact', s))
+ 
+     def is_interacting(self):
+         r"""
+@@ -1344,7 +1344,7 @@ class Cell(Cell_generic):
+         return hasattr(self, 'interact')
+ 
+     def stop_interacting(self):
+-        """
++        r"""
+         Stops :func:`sagenb.notebook.interact.interact`\ ion for this
+         compute cell.
+ 
+--- build/pkgs/sagenb/src/sagenb/notebook/worksheet.py.orig	2018-05-22 10:01:48.000000000 -0600
++++ build/pkgs/sagenb/src/sagenb/notebook/worksheet.py	2018-10-17 14:41:08.634154908 -0600
+@@ -61,8 +61,8 @@ from flask_babel import gettext, lazy_ge
+ _ = gettext
+ 
+ # Set some constants that will be used for regular expressions below.
+-whitespace = re.compile('\s')  # Match any whitespace character
+-non_whitespace = re.compile('\S')
++whitespace = re.compile(r'\s')  # Match any whitespace character
++non_whitespace = re.compile(r'\S')
+ 
+ # The file to which the Sage code that will be evaluated is written.
+ CODE_PY = "___code___.py"
+--- src/sage/combinat/cluster_algebra_quiver/quiver_mutation_type.py.orig	2018-10-17 17:13:35.000000000 -0600
++++ src/sage/combinat/cluster_algebra_quiver/quiver_mutation_type.py	2018-10-25 14:14:33.033253539 -0600
+@@ -2023,7 +2023,7 @@ class QuiverMutationType_Reducible(Quive
+ 
+     @cached_method
+     def class_size(self):
+-        """
++        r"""
+         If it is known, the size of the mutation class of all quivers
+         which are mutation equivalent to the standard quiver of
+         ``self`` (up to isomorphism) is returned.
+--- src/sage/combinat/crystals/alcove_path.py.orig	2018-10-17 17:13:35.000000000 -0600
++++ src/sage/combinat/crystals/alcove_path.py	2018-10-25 15:37:04.294360718 -0600
+@@ -389,7 +389,7 @@ class CrystalOfAlcovePaths(UniqueReprese
+ 
+         One can compute all vertices of the crystal by finding all the
+         admissible subsets of the `\lambda`-chain  (see method
+-        is_admissible, for definition).  We use the breath first
++        is_admissible, for definition).  We use the breadth first
+         search algorithm.
+ 
+         .. WARNING::
+--- src/sage/homology/homology_group.py.orig	2018-10-17 17:13:47.000000000 -0600
++++ src/sage/homology/homology_group.py	2018-10-25 15:54:54.683421705 -0600
+@@ -109,7 +109,7 @@ class HomologyGroup_class(AdditiveAbelia
+             sage: from sage.homology.homology_group import HomologyGroup
+             sage: H = HomologyGroup(7, ZZ, [4,4,4,4,4,7,7])
+             sage: H._latex_()
+-            'C_{4}^{5} \\times C_{7} \\times C_{7}'
++            'C_{4}^{5} \times C_{7} \times C_{7}'
+             sage: latex(HomologyGroup(6, ZZ))
+             \ZZ^{6}
+         """