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-fes.patch

@@ -1,7 +1,7 @@
 diff -up src/module_list.py.orig src/module_list.py
---- src/module_list.py.orig	2018-08-29 08:35:19.927079956 -0600
-+++ src/module_list.py	2018-08-29 10:41:05.127643255 -0600
-@@ -471,10 +471,10 @@ ext_modules = [
+--- src/module_list.py.orig	2019-01-16 09:45:43.332740109 -0700
++++ src/module_list.py	2019-01-16 09:46:10.613250567 -0700
+@@ -470,10 +470,10 @@ ext_modules = [
      Extension('sage.libs.ecl',
                sources = ["sage/libs/ecl.pyx"]),