Make GSL random distributions initialize with the sage random state functions

This means that Sage's randstate set_random_seed function will make the
GSL distributions also be predictable (for doctests, random matrices, etc.)
Delete #random on some matrix constructor doctests that now depend on Sage's random state
Disable use of weak symbols on Cygwin64 in PPL.
Trac 16855: make finite fields satisfy comparison by identity
Trac 16855: correct option implemention -> impl
Correct derivative of bessel_K
Fix error converting solutions to dict when solving for multiple variables.
Refactor some methods for finite fields elements.
Cleanup unused code and move doctests for finite field elements.
Typo in moved doctest.
Merge back changes from ticket 16930.
New code produce different square root choices for FF elements.
Use new style Python error formatting.
Typo in error text... and update three other errors syntax.
Merge branch 'develop' into t/15887/ticket/15887
Conflicts:
	src/sage/gsl/probability_distribution.pyx
Fix output precision.
Change the max seed to 2^31.
Fix doctests for new random output.
Added polytopes tutorial to thematic tutorials
Added polytope tutorial to list of tutorials