Replace strdup() with pstrdup(), to avoid leaking memory.

It's been like this since the seg module was introduced, so backpatch to
8.2 which is the oldest supported version.

contrib/seg/seg.c

@@ -892,7 +892,7 @@ restore(char *result, float val, int n)
 	*p = '\0';
 
 	/* get the exponent */
-	strtok(strdup(result), "e");
+	strtok(pstrdup(result), "e");
 	exp = atoi(strtok(NULL, "e"));
 
 	if (exp == 0)