Fix typo
UnXFAIL test_real_Pow

    This test doesn't fail anymore.  And mentioned in docstring
    statements (pi/log(x)).is_real is NOT True (with no assumptions
    on x) long time ago, since commit 6ee8b34.
Fix and UnXFAIL test_rational_products
Fix and UnXFAIL test_wallis_product
Fix and UnXFAIL test_gosper_nan
Karr convention: change limits in doit() for symbolic integers

    This is a small modification for commit dda493
Merge pull request #2315 from skirpichev/misc

Misc small fixes
Merge branch 'master' into 1756-division-by-order
Drop redundant tests, add test for 1/O(x, x, oo)
Refactor loop: while denominator.is_Order
Refactor loop: while prefactor.is_Order
Refactor loop while s1.getn() < n