perf_counter tools: Introduce stricter C code checking

Tighten up our C code requirements:

 - disallow warnings
 - disallow declarations-mixed-with-statements
 - require proper prototypes
 - require C99 (with gcc extensions)

Fix up a ton of problems these measures unearth:

 - unused functions
 - needlessly global functions
 - missing prototypes
 - code mixed with declarations

Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Mike Galbraith <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Corey Ashford <[email protected]>
Cc: Marcelo Tosatti <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: John Kacur <[email protected]>
Cc: Steven Rostedt <[email protected]>
LKML-Reference: <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
diff --git a/Documentation/perf_counter/builtin-help.c b/Documentation/perf_counter/builtin-help.c
index 6616de0..d2bd317 100644
--- a/Documentation/perf_counter/builtin-help.c
+++ b/Documentation/perf_counter/builtin-help.c
@@ -399,7 +399,7 @@
  * HTML.
  */
 #ifndef open_html
-void open_html(const char *path)
+static void open_html(const char *path)
 {
 	execl_perf_cmd("web--browse", "-c", "help.browser", path, NULL);
 }