eliminate gcc dependency for testing char signedness in limits.h

diff --git a/include/limits.h b/include/limits.h
index f8314a5..54d1940 100644 (file)
--- a/include/limits.h
+++ b/include/limits.h
@@ -9,7 +9,7 @@
 
 /* Support signed or unsigned plain-char */
 
-#ifdef __CHAR_UNSIGNED__
+#if '\0'-1 > 0
 #define CHAR_MIN 0
 #define CHAR_MAX 255
 #else