attach to parent console and provide stdout/stderr for GUI app. under Windows
fixup issue 767 & func.cc cleanup
1) fixed last cases of duplicate calls to getArgValue() in builtin_lookup() and instantiate();
2) make sin_degrees() & cos_degrees() separate functions to use in other parts of code;
3) cleaned most of gcc warnings in func.cc
Merge pull request #823 from tim-caper/func.cc

fixup issue 767 & func.cc cleanup
Merge branch 'winconsole2' of git://github.com/tim-caper/openscad into tim-caper-winconsole2

Conflicts:
	src/openscad.cc
Merge branch 'master' of github.com:openscad/openscad into test3dexport
Merge branch 'test3dexport' of github.com:openscad/openscad into test3dexport
allow alternate image comparison tool diffpng based on Hector Yee's algorithm