Add -Wno-implicit-function-declaration to a few places to work w D122983

D122983 intends to make these cases a 'warning as error' in C11 and C17
modes, and an attempt to set these to C99 mode caused more failures due
to included-files no longer containing certain symbols.  This patch just
adds the warning-opt-out to the tests that matter.  See for details.

Differential Revision:
5 files changed