STY: Fix some multiline C comments in npy_3kcompat.h.
Merge pull request #4545 from charris/style-fix

STY: Fix some multiline C comments in npy_3kcompat.h.
MAINT: fix unused variable warning
MAINT: ignore some more generated C files
Merge pull request #4365 from larsmans/c-fixes

MAINT: fix unused variable warning