Remove is_Add heuristic from limit()
UnXFAIL Wester test X8
UnXFAIL Wester test U10 (fixed with PR#2502)
Fix comparison of +/-oo with complex numbers (issue 4128)
More tests for oo/-oo (rhs of inequations)
Merge pull request #2734 from skirpichev/complex-cmp-oo

Fix comparison of oo/-oo with complex numbers (issue 4128)
Merge pull request #2741 from skirpichev/unxfail-wester-X8-U10

UnXFAIL Wester tests X8 and U10
Merge pull request #2740 from skirpichev/limits-remove-is_Add

Remove is_Add heuristic from limit()
make sure Matrix([]) == Matrix([[]])

constant_sytem must recognize when A is a zero-sized matrix (or
else row_join and col_join need to be modified to allow joins
for a zero-sized matrix and something else, e.g.
Matrix(0,1,[]).row_join(eye(1))).
Merge pull request #2761 from smichr/mat0

make sure Matrix([]) == Matrix([[]])
fix test and revert collecting intervals
Merge branch 'master' into isolve
Updated prerequisite for docs installations.
solvers.inequalities: updated docs and solvers.__init__