[PATCH] Provide dri shared library building and SDK installation.

[Luc Verhaegen]

Patch cherry-picked from my dri-sdk-7.8 branch against current head 
(edb5253dfa). An earlier full build through of all drivers (except 
nouveau, i will play with its expansive libdrm dependencies later) 
showed it to be an exact match still.

This patch, while not harming or hampering anything or anyone, gives us 
the ability to maintain and build DRI drivers out of tree for those so 
inclined. Build system additions only. No adverse effects. Everybody 
wins.

I intend to provide changes as needed, I hope to at least manage to 
maintain released versions in the long term.

For those wanting a test run, please check out the 7.8 version of the 
SDK and the drivers in my cgit.freedesktop.org repos.

Luc Verhaegen.