[testsuite] tsvc: skip include malloc.h when unavailable

[testsuite] tsvc: skip include malloc.h when unavailable

tsvc tests all fail on systems that don't offer a malloc.h, other than
those that explicitly rule that out.  Use the preprocessor to test for
malloc.h's availability.

tsvc.h also expects a definition for struct timeval, but it doesn't
include sys/time.h.  Add a conditional include thereof.

for  gcc/testsuite/ChangeLog

	* gcc.dg/vect/tsvc/tsvc.h: Test for and conditionally include
	malloc.h and sys/time.h.

(cherry picked from commit 2f20d6296087cae51f55eeecb3efefe786191fd6)