Fixed runtime error on older gcc/g++ (<4.9) where std::reg_ex is non-standards compliant and produced a regex compile fail.  This new simpler regex does not trip up even broken libstdc++ std::regex implementations.
Fixed runtime error on older gcc/g++ (<4.9) where std::reg_ex is non-standards compliant and produced a regex compile fail.  This new simpler regex does not trip up even broken libstdc++ std::regex implementations.

Summary: Fixes phabricator issue T56

Test Plan: make check on Ubuntu 14.04 / 14.05 (Travis equivalent)

Reviewers: #bitcoin_abc, deadalnix, freetrader, sickpig, kyuupichan, awemany, O1 Bitcoin ABC

Reviewed By: #bitcoin_abc, deadalnix, O1 Bitcoin ABC

Differential Revision: https://reviews.bitcoinabc.org/D290

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