explicitly set QMAKE_PKGCONFIG_NAME

otherwise qmake will just take TARGET and lowercase and capitalize it,
which not only looks weird, but also does not match the Requires: fields
we generate.

Change-Id: I4a070ff256fffd2b780acb0361d4213d0032dbb9
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Dihan Wickremasuriya <nayomal@gmail.com>
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>

mkspecs/features/qt_module.prf

@@ -206,6 +206,7 @@ unix {
 }
 
 unix|win32-g++* {
+    QMAKE_PKGCONFIG_NAME = $$replace(TARGET, ^Qt, Qt$$section(VERSION, ., 0, 0))
     for(i, MODULE_DEPENDS): \
         QMAKE_PKGCONFIG_REQUIRES += $$replace(QT.$${i}.name, ^Qt, Qt$$eval(QT.$${i}.MAJOR_VERSION))
     isEmpty(QMAKE_PKGCONFIG_DESCRIPTION): \