syncqt: paths are not properly made relative on msysgit Perl

Under msysgit Perl, it appears that fixPaths() can end up getting input like this: c:/path/to/header
C:/path/to/header

In cases like this, abs2rel() will return a long (and incorrect) relative path due to the difference in case being recognized as a difference in path. This can be fixed by modifying normalizePath() to handle input paths that begin with a driver letter (but not a slash).