user: implement mlibc as the libc, finally.

It's finally done..

Signed-off-by: kaguya <vpshinomiya@protonmail.com>

user/include/mlibc/options/internal/generic/strings.cpp

@@ -0,0 +1,22 @@
+#include <ctype.h>
+
+#include <mlibc/strings.hpp>
+
+namespace mlibc {
+
+int strncasecmp(const char *a, const char *b, size_t size) {
+	for(size_t i = 0; i < size; i++) {
+		unsigned char a_byte = tolower(a[i]);
+		unsigned char b_byte = tolower(b[i]);
+		if(!a_byte && !b_byte)
+			return 0;
+		// If only one char is null, one of the following cases applies.
+		if(a_byte < b_byte)
+			return -1;
+		if(a_byte > b_byte)
+			return 1;
+	}
+	return 0;
+}
+
+} // namespace mlibc