Portability fixes,  with these changes I am able to build liblightgrep on FreeBSD.
Merge remote-tracking branch 'upstream/master'
Merge remote-tracking branch 'upstream/master'
Merge remote-tracking branch 'upstream/master'
Merge pull request #6 from LightboxTech/master

Check bison version
Merge branch 'master' of github.com:jonstewart/liblightgrep
Merge pull request #3 from LightboxTech/master

Merge pull request #10 from uckelman/master
Merge branch 'master' of github.com:LightboxTech/liblightgrep
Merge branch 'master' of github.com:uckelman/liblightgrep
Use std::istringstream, std::ostringstream instead of std::stringstream
when we don't need both input and output.
Merge branch 'master' of https://github.com/ant1/liblightgrep