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>.

gcc/ipa-fnsummary.c

@@ -52,6 +52,7 @@ along with GCC; see the file COPYING3.  If not see
    inlined performs analysis via its analyze_function method. */
 
 #include "config.h"
+#define INCLUDE_VECTOR
 #include "system.h"
 #include "coretypes.h"
 #include "backend.h"
@@ -82,7 +83,6 @@ along with GCC; see the file COPYING3.  If not see
 #include "gimplify.h"
 #include "stringpool.h"
 #include "attribs.h"
-#include <vector>
 #include "tree-into-ssa.h"
 
 /* Summaries.  */