parsers.c: remove warning: 'size' may be used uninitialized in this function

Some compilers / compiler options (such as gcc 4.7) would emit warnings:

mercurial/parsers.c: In function 'pack_dirstate':
mercurial/parsers.c:306:18: warning: 'size' may be used uninitialized in this function [-Wmaybe-uninitialized]
mercurial/parsers.c:306:12: warning: 'mode' may be used uninitialized in this function [-Wmaybe-uninitialized]

It is apparently not smart enough to figure out how the 'err' arithmetics makes
sure that it can't happen.

'err' is now replaced with simple checks and goto. That might also help the
optimizer when it is inlining getintat().

mercurial/parsers.c

@@ -307,7 +307,6 b' static PyObject *pack_dirstate(PyObject '
 		Py_ssize_t len, l;
 		PyObject *o;
 		char *s, *t;
-		int err;
 
 		if (!PyTuple_Check(v) || PyTuple_GET_SIZE(v) != 4) {
 			PyErr_SetString(PyExc_TypeError, "expected a 4-tuple");
@@ -319,10 +318,11 b' static PyObject *pack_dirstate(PyObject '
 			goto bail;
 		}
 		*p++ = *s;
-		err = getintat(v, 1, &mode);
-		err |= getintat(v, 2, &size);
-		err |= getintat(v, 3, &mtime);
-		if (err)
+		if (getintat(v, 1, &mode) == -1)
+			goto bail;
+		if (getintat(v, 2, &size) == -1)
+			goto bail;
+		if (getintat(v, 3, &mtime) == -1)
 			goto bail;
 		if (*s == 'n' && mtime == (uint32_t)now) {
 			/* See dirstate.py:write for why we do this. */