Add a port for 'tre', an LGPL'ed regex library. From the port's
TRE is a lightweight, robust, and efficient POSIX compliant regexp
matching library supporting:
- approximate (fuzzy) matching,
- strict standards conformance,
- predicable and modest memory consumption,
- wide-character and multibyte character support,
- binary pattern and data support,
- thread-safe implementation.
At the core of TRE is a new algorithm for regular expression matching
with submatch addressing. The algorithm uses linear worst-case time
in the length of the text being searched, and quadratic worst-case
time in the length of the used regular expression.