QmakeGlobals::expandEnvVars: Make sane
QmakeGlobals::expandEnvVars: Make sane

Use indexOf() to match individual characters, which is a lot faster than
QRegExp. As a side effect, don't try to expand what we just inserted.

Change-Id: I964fbd92055f2f2649e7d8ed5739cf1fc7cae927
Reviewed-by: Oswald Buddenhagen <6a8868beda3e139b5ac22b2534a23d3e6ba81819@digia.com>
Reviewed-by: Daniel Teske <d8a411aec9a206efedb4d45b75fe8d13f1e2b628@digia.com>

Distrotech/qtcreator,Distrotech/qtcreator,danimo/qt-creator,kuba1/qtcreator,danimo/qt-creator,martyone/sailfish-qtcreator,xianian/qt-creator,kuba1/qtcreator,danimo/qt-creator,farseerri/git_code,danimo/qt-creator,martyone/sailfish-qtcreator,Distrotech/qtcreator,xianian/qt-creator,farseerri/git_code,martyone/sailfish-qtcreator,amyvmiwei/qt-creator,danimo/qt-creator,farseerri/git_code,xianian/qt-creator,xianian/qt-creator,kuba1/qtcreator,kuba1/qtcreator,kuba1/qtcreator,xianian/qt-creator,martyone/sailfish-qtcreator,danimo/qt-creator,amyvmiwei/qt-creator,martyone/sailfish-qtcreator,martyone/sailfish-qtcreator,kuba1/qtcreator,AltarBeastiful/qt-creator,AltarBeastiful/qt-creator,farseerri/git_code,danimo/qt-creator,martyone/sailfish-qtcreator,kuba1/qtcreator,kuba1/qtcreator,amyvmiwei/qt-creator,AltarBeastiful/qt-creator,AltarBeastiful/qt-creator,amyvmiwei/qt-creator,danimo/qt-creator,martyone/sailfish-qtcreator,xianian/qt-creator,xianian/qt-creator,xianian/qt-creator,Distrotech/qtcreator,amyvmiwei/qt-creator,farseerri/git_code,kuba1/qtcreator,AltarBeastiful/qt-creator,martyone/sailfish-qtcreator,AltarBeastiful/qt-creator,amyvmiwei/qt-creator,amyvmiwei/qt-creator,amyvmiwei/qt-creator,farseerri/git_code,Distrotech/qtcreator,AltarBeastiful/qt-creator,xianian/qt-creator,danimo/qt-creator,farseerri/git_code,Distrotech/qtcreator,Distrotech/qtcreator,AltarBeastiful/qt-creator,farseerri/git_code