Adding 'weka'.
Fixing vaapi-vdpau build with newer mesa.
Note about the source of previous build fix in glext85
shishi: fix compilation on darwin
guile: remove gcc_s dep, skip check on darwin
irssi: fix build on darwin

* use `gccApple` (so we can cope with `-no-cpp-precompile`)
* add `libintlOrEmpty`
amdappsdk: Fix download urls and some other things, so derivations for older sdk versions now build succesfully
Merge pull request #651 from lovek323/shishi

shishi: fix compilation on darwin
Merge pull request #652 from lovek323/guile

guile: remove gcc_s dep, skip check on darwin
Merge pull request #653 from lovek323/irssi

irssi: fix build on darwin
Merge pull request #656 from offlinehacker/amdappsdk_fix

amdappsdk: Fix download urls and some other things, so derivations for older sdk versions now build succesfully