Bug fix: line number text to respect the left margin; performance improvement: do not calculate available width and hight for each line, do it once
Bug fix: line number text to respect the left margin; performance improvement: do not calculate available width and hight for each line, do it once

hlamer/qutepart,andreikop/qutepart,hlamer/qutepart,andreikop/qutepart,andreikop/qutepart,andreikop/qutepart,hlamer/qutepart,andreikop/qutepart,hlamer/qutepart,hlamer/qutepart,hlamer/qutepart,hlamer/qutepart,hlamer/qutepart,andreikop/qutepart,andreikop/qutepart,hlamer/qutepart,hlamer/qutepart,andreikop/qutepart,andreikop/qutepart,hlamer/qutepart,andreikop/qutepart,andreikop/qutepart