feat: expand user mode, add DOOM game, add manpages

programs/include/libc/strings.h

@@ -0,0 +1,17 @@
+#ifndef _LIBC_STRINGS_H
+#define _LIBC_STRINGS_H
+
+#include <stddef.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+int strcasecmp(const char *s1, const char *s2);
+int strncasecmp(const char *s1, const char *s2, size_t n);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _LIBC_STRINGS_H */