twn_util_c.h: internal profiling api

src/twn_util_c.h

@@ -23,6 +23,9 @@ _Noreturn void die_abruptly(void);
 /* note: you must free the returned string */
 char *expand_asterisk(const char *mask, const char *to);
 
+void profile_start(char profile[const static 1]);
+void profile_end(char profile[const static 1]);
+
 /* http://www.azillionmonkeys.com/qed/sqroot.html */
 static inline float fast_sqrt(float x)
 {