perf tools: Move event synthesizing routines to separate header

Those are the only routines using the perf_event__handler_t typedef and
are all related, so move to a separate header to reduce the header
dependency tree, lots of places were getting event.h and even stdio.h,
limits.h indirectly, so fix those as well.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lkml.kernel.org/n/tip-yvx9u1mf7baq6cu1abfhbqgs@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/arch/x86/util/tsc.c

@@ -8,6 +8,8 @@
 #include <linux/types.h>
 #include <asm/barrier.h>
 #include "../../../util/debug.h"
+#include "../../../util/event.h"
+#include "../../../util/synthetic-events.h"
 #include "../../../util/tsc.h"
 
 int perf_read_tsc_conversion(const struct perf_event_mmap_page *pc,