perf tools: Factorize high level dso helpers

Factorize multiple definitions of high level dso helpers into the
symbol source file.

The side effect is a general export of the verbose and eprintf
debugging helpers into a new file dedicated to debugging purposes.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Brice Goglin <Brice.Goglin@inria.fr>

tools/perf/util/debug.h

@@ -0,0 +1,5 @@
+/* For debugging general purposes */
+
+extern int verbose;
+
+int eprintf(const char *fmt, ...) __attribute__((format(printf, 1, 2)));