TravisCI specific build improvements:

When compiling on Travis:
 * display information about repo and branch that is being built.
 * For C/C++ code: define TRAVIS_CI_BUILD for C and C++ code.
 * For C/C++ code: define RIPPLE_MASTER_BUILD for any builds made
   against the Ripple organizational repo.
[FOLD/TX-REFAC] WalletAdd Transactor journal
[FOLD/TX-REFAC] TrustSet Transactor journal
[FOLD/TX-REFAC] RegularKeySet Transactor journal
[FOLD/TX-REFAC] Payment Transactor journal