Adds base64 support via mbedtls

This is inspered in the work done at: #1123

src/utils/base64.h

@@ -0,0 +1,16 @@
+
+
+namespace modsecurity {
+namespace Utils {
+
+class Base64 {
+ public:
+    Base64() { }
+
+    static std::string encode(std::string& data);
+    static std::string decode(std::string& data);
+};
+
+
+}  // namespace Utils
+}  // namespace modsecurity