add some rudimentary memory manipulation functions

c_os/lib/MyStdLib.cc

@@ -0,0 +1,7 @@
+#include "MyStdLib.h"
+
+void mymemset(char* destination, char value, unsigned int bytes) {
+    for (unsigned int byte = 0; byte < bytes; ++byte) {
+        *(destination + byte) = value;
+    }
+}