gcc 6.3 warning

[Vince Weaver]

papi_preset.c: In function ‘check_derived_events’: papi_preset.c:513:19: warning: ‘__s’ may be used uninitialized in this function [-Wmaybe-uninitialized] int val = atoi(&subtoken[1]); ^~~~ papi_preset.c:464:1: note: ‘__s’ was declared here ops_string_merge(char *original, char insertion, int replaces, int start_index) { ^~~~

[Vince Weaver]

Fixed by 211228bab1aedacd8df3c3c78d2cf47fecc7cab5