using QMAKE_PKGCONFIG_FILE for Qt5 builds


git-svn-id: svn://svn.code.sf.net/p/qwt/code/trunk@2028 29e17f8d-cf37-471e-a288-72cc03a76eda
pkgconfig rules changed again


git-svn-id: svn://svn.code.sf.net/p/qwt/code/trunk@2029 29e17f8d-cf37-471e-a288-72cc03a76eda
svn:ignore for accidental pkgconfig dirs generated by Qt4 qmake


git-svn-id: svn://svn.code.sf.net/p/qwt/code/trunk@2030 29e17f8d-cf37-471e-a288-72cc03a76eda