[windows] MySQL include dir precedes INCLUDEPATH of Qt module project in compiler command-line args

Combination of the following conditions result in wrong include paths order:

• mkspecs/qmodule.pri appends some paths to INCLUDEPATH, e.g. this is the case on Windows for MySql and PostgreSql include dirs, when they are provided via configure -I flags
• qmake project is Qt module with typical .qmake.conf

In this case, INCLUDEPATH from qmodule.pri take priority over INCLUDEPATH defined in project. This breaks compilation of QtWebKit on Windows in CI (see [1]), where header "decimal.h" from MySQL is erroneously included instead of local "Decimal.h" header.

In attachment there is simple Qt module, reproducing this bug.

[1] http://testresults.qt.io/logs/qt/qtwebkit/8b1cd48bda010279ef2a2333e0f4f4b1fd43a29b/WindowsWindows_8_1x86_64WindowsWindows_8_1x86_64MSVC2013DebugAndRelease_Release_OpenGLDynamic/f9c78239237300336bf7587e54954be7299a13ab/buildlog.txt.gz