QwtSymbol::Pixmap and pinpoint translations fixed, when being cached


git-svn-id: svn://svn.code.sf.net/p/qwt/code/branches/qwt-6.1@1979 29e17f8d-cf37-471e-a288-72cc03a76eda
avoiding of pointless tick label calculations for multiturn knobs


git-svn-id: svn://svn.code.sf.net/p/qwt/code/branches/qwt-6.1@1982 29e17f8d-cf37-471e-a288-72cc03a76eda
performance issues of circular scales fixed


git-svn-id: svn://svn.code.sf.net/p/qwt/code/branches/qwt-6.1@1985 29e17f8d-cf37-471e-a288-72cc03a76eda
early blocking of ticks with length 0


git-svn-id: svn://svn.code.sf.net/p/qwt/code/branches/qwt-6.1@1987 29e17f8d-cf37-471e-a288-72cc03a76eda