MINIFICPP-1239 Use <regex> except in gcc < 4.9

[fgerlits]

Thank you for submitting a contribution to Apache NiFi - MiNiFi C++.

Description of PR

We should use the regular expression implementation from the STL whenever we can, which means for all compilers except gcc versions before 4.9.

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[hunyadi-dev]

Looks good to me.

[arpadboda]

LGTM