QwtPlot::canvasMap: margins fixed in case of disabled axes


git-svn-id: svn://svn.code.sf.net/p/qwt/code/branches/qwt-6.1-multiaxes@1974 29e17f8d-cf37-471e-a288-72cc03a76eda
bode example test code reverted


git-svn-id: svn://svn.code.sf.net/p/qwt/code/branches/qwt-6.1-multiaxes@1975 29e17f8d-cf37-471e-a288-72cc03a76eda
QwtInterval::widthL added


git-svn-id: svn://svn.code.sf.net/p/qwt/code/branches/qwt-6.1-multiaxes@1978 29e17f8d-cf37-471e-a288-72cc03a76eda