ipa-fnsummary: Include <vector> the proper way

ipa-fnsummary: Include <vector> the proper way

This fixes a bootstrap error with clang 10 that would complain
  /usr/include/c++/v1/typeinfo:346:5: error: no member named
  'fancy_abort' in namespace 'std::__1'; did you mean simply
  'fancy_abort'?
It mirrors how this is handled in gcov.c and indirectly includes
<vector> via system.h.

gcc/ChangeLog:

	* ipa-fnsummary.c (INCLUDE_VECTOR): Define.
	Remove direct inclusion of <vector>.