v1.2.8

Improved support for builds that use clang's link time optimization.
Added some flags as usual.
Beefed up the parsing so that it handles (non-nested) -Wl,start-group ... -Wl,end-group command line options.
Added an undocumented executable gparse which just parses the command line as would gclang or gclang++
and just prints the result rather than acting upon the input.