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-lcalc.patch

@@ -1,20 +1,12 @@
-diff -up src/sage/libs/lcalc/lcalc_Lfunction.pxd.orig src/sage/libs/lcalc/lcalc_Lfunction.pxd
---- src/sage/libs/lcalc/lcalc_Lfunction.pxd.orig	2018-05-05 16:21:24.000000000 -0600
-+++ src/sage/libs/lcalc/lcalc_Lfunction.pxd	2018-05-22 13:31:10.717337490 -0600
-@@ -1,6 +1,6 @@
- # Lcalc requires GNU extensions, it does not strictly conform to any
- # C++ standard: https://trac.sagemath.org/ticket/23341
--# distutils: extra_compile_args = -std=gnu++98
-+# distutils: extra_compile_args = -std=gnu++11
+diff -up src/module_list.py.orig src/module_list.py
+--- src/module_list.py.orig	2019-01-16 09:42:41.397004883 -0700
++++ src/module_list.py	2019-01-16 09:45:43.332740109 -0700
+@@ -513,7 +513,7 @@ ext_modules = [
+     Extension('sage.libs.lcalc.lcalc_Lfunction',
+               sources = ['sage/libs/lcalc/lcalc_Lfunction.pyx'],
+               libraries = ['m', 'ntl', 'Lfunction'],
+-              extra_compile_args=["-O3", "-ffast-math"],
++              extra_compile_args=["-std=gnu++11", "-ffast-math"],
+               language = 'c++'),
  
- cdef extern from "lcalc_sage.h":
-     ctypedef struct doublevec "std::vector<double>":
-diff -up src/sage/libs/lcalc/lcalc_sage.h.orig src/sage/libs/lcalc/lcalc_sage.h
---- src/sage/libs/lcalc/lcalc_sage.h.orig	2018-05-05 16:21:24.000000000 -0600
-+++ src/sage/libs/lcalc/lcalc_sage.h	2018-05-22 13:30:32.012839737 -0600
-@@ -1,4 +1,4 @@
--#include "libLfunction/L.h"
-+#include "Lfunction/L.h"
- 
- int *new_ints(int l)
- {
+     Extension('sage.libs.libecm',