GCC 6 puts out warnings in a different location then GCC 5. Move the
DIAG macros so that the warnings are supressed for both compilers.
ChangeLog:
* soft-fp/fmasf4.c: Add include of sys/cdefs.h.
Move DIAG_PUSH_NEEDS_COMMENT, DIAG_IGNORE_NEEDS_COMMENT to front of
file, move DIAG_POP_NEEDS_COMMENT to end of file.
* soft-fp/fmadf4.c: Ditto.
* soft-fp/fmatf4.c: Ditto.