The patch fixes errors that occur if a path to default compiler has spaces or if an argument with spaces is given to compiler (e.g. via -I).
The precedent: running scan-build that uses clang compiled by VS ends up with
error: error reading 'Files\Microsoft'
error: error reading 'Visual'
error: error reading 'Studio'
error: error reading '11.0\VC\include'
Ok to commit?
I think we can just pass true to quotewords' 'keep' parameter.