We don't use msg in yyerror, don't name it.
C++11: Even though we can't use <thread> everywhere yet, we can get
cleaner code by using std::vector instead of boost::thread_group.
Successfully test for Darwin and add -stdlib=libc++ to CXXFLAGS. This gets the library to build successfully on MacOS X 10.8 with './configure CC=cc CXX=c++' and macports Boost and ICU. This is not sufficent to build and run the unit tests, however.
Merge branch 'master' of github.com:uckelman/liblightgrep
Merge pull request #3 from jonstewart/master

configure change for Mac builds, plus some changes from Joel