Avro C - avro_value_cmp_fast() may return garbage value for AVRO_STRING comparison

Compiler shows a warning that variables may be used uninitialized in avro_value_cmp_fast():

/home/user/avro-trunk/lang/c/src/value.c: In function 'avro_value_cmp_fast':
/home/user/avro-trunk/lang/c/src/value.c:387:13: warning: 'size2' may be used uninitialized in this function [-Wuninitialized]
/home/user/avro-trunk/lang/c/src/value.c:387:13: warning: 'size1' may be used uninitialized in this function [-Wuninitialized]
/home/user/avro-trunk/lang/c/src/value.c:388:11: warning: 'buf1' may be used uninitialized in this function [-Wuninitialized]
/home/user/avro-trunk/lang/c/src/value.c:388:11: warning: 'buf2' may be used uninitialized in this function [-Wuninitialized]

Examining the file shows that the warnings are real, and the variables size1, buf1, size2, buf2 should be loaded before they are used. The simple fix is to copy matching code from the function avro_value_equal_fast(). I will attach that code in an upcoming patch.

Cheers,
Vivek