Add strcasecmp() and strncasecmp()

strncasecmp() is present as strnicmp() but disabled. Make it available
and define strcasecmp() also. There is a only a small performance penalty
to having strcasecmp() call strncasecmp(), so do this instead of a
standalone function, to save code space.

Update the prototype in arch-specific headers as needed to avoid warnings.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/lib/string.c b/lib/string.c
index c3ad055..68f60be 100644
--- a/lib/string.c
+++ b/lib/string.c
@@ -21,14 +21,13 @@
 #include <malloc.h>
 
 
-#if 0 /* not used - was: #ifndef __HAVE_ARCH_STRNICMP */
 /**
- * strnicmp - Case insensitive, length-limited string comparison
+ * strncasecmp - Case insensitive, length-limited string comparison
  * @s1: One string
  * @s2: The other string
  * @len: the maximum number of characters to compare
  */
-int strnicmp(const char *s1, const char *s2, size_t len)
+int strncasecmp(const char *s1, const char *s2, size_t len)
 {
 	/* Yes, Virginia, it had better be unsigned */
 	unsigned char c1, c2;
@@ -52,7 +51,16 @@
 	}
 	return (int)c1 - (int)c2;
 }
-#endif
+
+/**
+ * strcasecmp - Case insensitive string comparison
+ * @s1: One string
+ * @s2: The other string
+ */
+int strcasecmp(const char *s1, const char *s2)
+{
+	return strncasecmp(s1, s2, -1U);
+}
 
 char * ___strtok;