[glacier] Create lib with scaffolding string class.

lib/glacier/string/string.h

@@ -0,0 +1,18 @@
+#pragma once
+
+#include <stdint.h>
+
+namespace glcr {
+
+class String {
+ public:
+  String(const char* cstr);
+
+  bool operator==(const String& str);
+
+ private:
+  char* cstr_;
+  uint64_t length_;
+};
+
+}  // namespace glcr