perf tools: Fix old GCC build error in 'get_srcline'

trace-event-parse.c:parse_proc_kallsyms()

    Old GCC (4.4.2) does not see through the code flow of get_srcline() and
gets confused about the status of 'file' and 'line':

    CC       /tmp/build/perf/util/srcline.o
  cc1: warnings being treated as errors
  util/srcline.c: In function ¿get_srcline¿:
  util/srcline.c:226: error: ¿file¿ may be used uninitialized in this function
  util/srcline.c:227: error: ¿line¿ may be used uninitialized in this function
  make[1]: *** [/tmp/build/perf/util/srcline.o] Error 1
  make: *** [install] Error 2
  make: Leaving directory `/home/acme/git/linux/tools/perf'
  [acme@fedora12 linux]$

Help out GCC by initializing 'file' and 'line'.
Signed-off-by: David Ahern <dsahern@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@gmail.com>
Link: http://lkml.kernel.org/n/tip-h8k7h49z3cndqgjdftkmm9f8@git.kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/srcline.c

@@ -223,8 +223,8 @@ static int addr2line(const char *dso_name, unsigned long addr,
 
 char *get_srcline(struct dso *dso, unsigned long addr)
 {
-	char *file;
-	unsigned line;
+	char *file = NULL;
+	unsigned line = 0;
 	char *srcline;
 	char *dso_name = dso->long_name;
 	size_t size;