Fix fglmtools docstring.

Without this fix, pypy reports SyntaxError.
Add xrange (=range) to py3 compatibility list
Revert back xrange's after merge of PR #2318
xrange([0-9]) and xrange([0-9], [0-9]) -> range
Add imports xrange from sympy.core.compatibility
Merge pull request #2335 from jrioux/polys

Fix fglmtools docstring.
Merge pull request #2336 from skirpichev/fix-xrange-regression

Fix regressions, related to xrange -> range conversion in PR #2318
Unbundle mpmath: Kill mpmath source tree
Unbundle mpmath: Drop mpmath documentation
Unbundle mpmath: Correct list of modules and tests in setup.py
Unbundle mpmath: Fix imports
Unbundle mpmath: install python-mpmath
Unbundle mpmath: drop adapt_path.py script
Unbundle mpmath: drop workarrounds in bin/coverage_*
Unbundle mpmath: drop mpmath from blacklist of runtests.py
Unbundle mpmath: drop mpmath exclude from code quality tests
Unbundle mpmath: don't filter out mpmath directory in setup.py
Unbundle mpmath: document mpmath installation