This commit fixes quite a few odd things in regex code:
* Lack of encapsulation.
* Non-method functions for matching without retrieving all groups.
* Regex class being copyable without proper copy-constructor (potential UAF
and double free due to pointer members m_pc and m_pce).
* Redundant SMatch::m_length, which always equals to match.size() anyway.
* Weird SMatch::size_ member which is initialized only by one of the three matching
functions, and equals to the return value of that function anyways.
* Several places in code having std::string value instead of reference.
C++ regex library proven to be unusable for gcc 4.8 and earlier version, so
reimplement code using PCRE library in order to build workable version of
unit_test executable for CentOS 7, RHEL 7, Ubuntu 14 and SUSE Linux 12.
