Move tolower() etc to ctype.h as per ISO C

src/include/ctype.h

@@ -0,0 +1,28 @@
+#ifndef _CTYPE_H
+#define _CTYPE_H
+
+/** @file
+ *
+ * Character types
+ */
+
+#define isdigit(c)	((c & 0x04) != 0)
+#define islower(c)	((c & 0x02) != 0)
+//#define isspace(c)	((c & 0x20) != 0)
+#define isupper(c)	((c & 0x01) != 0)
+
+static inline unsigned char tolower(unsigned char c)
+{
+	if (isupper(c))
+		c -= 'A'-'a';
+	return c;
+}
+
+static inline unsigned char toupper(unsigned char c)
+{
+	if (islower(c))
+		c -= 'a'-'A';
+	return c;
+}
+
+#endif /* _CTYPE_H */