cmake: cleanup cef.patch

remove unneeded hunks, because they could break the patch with newer
versions of CEF
cmake: remove unneded test in cef.patch

v2: fix patch
cmake: remove more hunks in cef.patch
ebuild: only install scalable icon

portage isn't generating png files from svg, so we should just install the svg file
Merge pull request #447 from karolherbst/ebuild

ebuild: only install scalable icon
Merge pull request #432 from karolherbst/cef_clean_patch

clean up cef.patch a bit