Initialize libsym early in trace.c to help the compiler.

Initialize libsym early in trace.c to help the compiler.

GCC 4.4.7 isn't smart enough to realize own_libsym will always be zero
when it sees the goto done which might jump over the initialization of
libsym. And so will produce a warning like:

cc1: warnings being treated as errors
trace.c: In function ‘ifunc_ret_hit’:
trace.c:1433: error: ‘libsym’ may be used uninitialized in this function