[testsuite] [analyzer] [vxworks] define __STDC_WANT_LIB_EXT1__ to 1

[testsuite] [analyzer] [vxworks] define __STDC_WANT_LIB_EXT1__ to 1

vxworks' headers use #if instead of #ifdef to test for
__STDC_WANT_LIB_EXT1__, so the definition in the analyzer test
strotok-cppreference.c catches a bug there, but not something it's
meant to catch or that we could fix in GCC, so amend the definition to
sidestep the libc bug.

for  gcc/testsuite/ChangeLog

	* c-c++-common/analyzer/strtok-cppreference.c
	(__STDC_WANT_LIB_EXT1__): Define to 1.