Update to sagemath 8.5.

Also:
- Bundle ipython again; Fedora version is too far ahead.  Also have to bundle
  prompt_toolkit since Fedora version is too far ahead of bundled ipython.
- Drop LANGUAGES variable setting, now ignored by the sagemath build system.
- Drop unused SAGE_CBLAS variable from /usr/bin/sage.
- Do not force the C locale when launching sagemath.
- Allow the user to override SAGE_DEBUG in /usr/bin/sage.
- Add -ecm, -giac, and -latte patches to fix interactions with external tools.
- Add -sigfpe patch from upstream.

sagemath-cremona.patch

@@ -1,6 +1,6 @@
 diff -up src/sage/databases/cremona.py.orig src/sage/databases/cremona.py
---- src/sage/databases/cremona.py.orig	2018-10-17 17:13:36.000000000 -0600
-+++ src/sage/databases/cremona.py	2018-10-25 13:24:02.644939224 -0600
+--- src/sage/databases/cremona.py.orig	2018-12-22 16:37:08.000000000 -0700
++++ src/sage/databases/cremona.py	2019-01-04 10:29:55.578694061 -0700
 @@ -53,7 +53,6 @@ from sage.misc.prandom import randint
  
  import sage.schemes.elliptic_curves.constructor as elliptic
@@ -9,7 +9,7 @@ diff -up src/sage/databases/cremona.py.orig src/sage/databases/cremona.py
  from sage.env import CREMONA_MINI_DATA_DIR, CREMONA_LARGE_DATA_DIR
  from sage.misc.all import walltime
  
-@@ -825,14 +824,6 @@ class MiniCremonaDatabase(SQLDatabase):
+@@ -835,14 +834,6 @@ class MiniCremonaDatabase(SQLDatabase):
              if N < self.largest_conductor():
                  message = "There is no elliptic curve with label " + label \
                      + " in the database"
@@ -24,7 +24,7 @@ diff -up src/sage/databases/cremona.py.orig src/sage/databases/cremona.py
              raise ValueError(message)
          ainvs = eval(c[0])
          data = {'cremona_label': label,
-@@ -1673,10 +1664,12 @@ def CremonaDatabase(name=None,mini=None,
+@@ -1683,10 +1674,12 @@ def CremonaDatabase(name=None,mini=None,
      if name is None and not set_global:
          return _db
      if set_global and name is None: