COMP: fix detection of qwt version (on precise QWT_MAJOR_VERSION is '6-svn'
COMP: fix detection of qwt version (on precise QWT_MAJOR_VERSION is '6-svn'

orfeotoolbox/OTB,orfeotoolbox/OTB,orfeotoolbox/OTB,orfeotoolbox/OTB,orfeotoolbox/OTB,orfeotoolbox/OTB