Some cleanup of cfopt.
Some cleanup of cfopt.

- renamed clear_link() to clear_link_and_mark_blocks_removable()
- renamed optimize_conds() to optimize_ifs()
- simplified has_*() implementations
- made some walker POST walker
- invalidate out edges
- and add some doxygen docu
- fixed some typos
- adapt to firm indentation style

MatzeB/libfirm,libfirm/libfirm,jonashaag/libfirm,8l/libfirm,killbug2004/libfirm,libfirm/libfirm,jonashaag/libfirm,MatzeB/libfirm,MatzeB/libfirm,davidgiven/libfirm,MatzeB/libfirm,killbug2004/libfirm,8l/libfirm,jonashaag/libfirm,killbug2004/libfirm,killbug2004/libfirm,killbug2004/libfirm,jonashaag/libfirm,8l/libfirm,8l/libfirm,MatzeB/libfirm,libfirm/libfirm,davidgiven/libfirm,jonashaag/libfirm,killbug2004/libfirm,davidgiven/libfirm,8l/libfirm,8l/libfirm,killbug2004/libfirm,davidgiven/libfirm,jonashaag/libfirm,davidgiven/libfirm,libfirm/libfirm,davidgiven/libfirm,MatzeB/libfirm,davidgiven/libfirm,libfirm/libfirm,8l/libfirm,MatzeB/libfirm,jonashaag/libfirm