Switch commoncpp2 to ucommon to solve dependency conflicts.

libccrtp was depending on commoncpp2, and have been replaced by a version
depending on ucommon as well.
diff --git a/jni/libucommon/sources/nossl/md5.h b/jni/libucommon/sources/nossl/md5.h
new file mode 100644
index 0000000..ff39264
--- /dev/null
+++ b/jni/libucommon/sources/nossl/md5.h
@@ -0,0 +1,34 @@
+/*  $OpenBSD: md5.h,v 1.16 2004/06/22 01:57:30 jfb Exp $    */
+
+/*
+ * This code implements the MD5 message-digest algorithm.
+ * The algorithm is due to Ron Rivest.  This code was
+ * written by Colin Plumb in 1993, no copyright is claimed.
+ * This code is in the public domain; do with it what you wish.
+ *
+ * Equivalent code is available from RSA Data Security, Inc.
+ * This code has been tested against that, and is equivalent,
+ * except that you don't need to include two pages of legalese
+ * with every copy.
+ */
+
+#ifndef _MD5_H_
+#define _MD5_H_
+
+#define MD5_BLOCK_LENGTH        64
+#define MD5_DIGEST_LENGTH       16
+#define MD5_DIGEST_STRING_LENGTH    (MD5_DIGEST_LENGTH * 2 + 1)
+
+typedef struct MD5Context {
+    uint32_t state[4];         /* state */
+    uint64_t count;            /* number of bits, mod 2^64 */
+    uint8_t buffer[MD5_BLOCK_LENGTH];  /* input buffer */
+} MD5_CTX;
+
+void     MD5Init(MD5_CTX *);
+void     MD5Update(MD5_CTX *, const uint8_t *, size_t);
+void     MD5Pad(MD5_CTX *);
+void     MD5Final(uint8_t [MD5_DIGEST_LENGTH], MD5_CTX *);
+void     MD5Transform(uint32_t [4], const uint8_t [MD5_BLOCK_LENGTH]);
+
+#endif /* _MD5_H_ */