FindQt4: Give precedence to QTDIR environment variable, if set.

Remove old search paths that aren't needed.

Keep using PATHS instead of HINTS because a Windows machine may have
a different Qt in its PATH and putting QTDIR and the registry entry
ahead of PATH could cause apps to fail when run.

Modules/FindQt4.cmake

@@ -486,11 +486,11 @@ get_filename_component(qt_install_version "[HKEY_CURRENT_USER\\Software\\trollte
 # check for qmake
 # Debian uses qmake-qt4
 # macports' Qt uses qmake-mac
-find_program(QT_QMAKE_EXECUTABLE NAMES qmake qmake4 qmake-qt4 qmake-mac PATHS
-  $ENV{QTDIR}/bin
-  "[HKEY_CURRENT_USER\\Software\\Trolltech\\Qt3Versions\\4.0.0;InstallDir]/bin"
-  "[HKEY_CURRENT_USER\\Software\\Trolltech\\Versions\\4.0.0;InstallDir]/bin"
-  "[HKEY_CURRENT_USER\\Software\\Trolltech\\Versions\\${qt_install_version};InstallDir]/bin"
+find_program(QT_QMAKE_EXECUTABLE NAMES qmake qmake4 qmake-qt4 qmake-mac
+  PATHS
+    ENV QTDIR
+    "[HKEY_CURRENT_USER\\Software\\Trolltech\\Versions\\${qt_install_version};InstallDir]"
+  PATH_SUFFIXES bin
   DOC "The qmake executable for the Qt installation to use"
 )