intel: Rename dri_ and intel_ symbols to drm_intel_.

I wanted to avoid doing this, as it's a bunch of churn, but there was a
conflict between the dri_ symbols in libdrm and the symbols that were in
Mesa in 7.2, which broke Mesa 7.2 AIGLX when the 2D driver had loaded new
libdrm symbols.  The new naming was recommended by cworth for giving the
code a unique prefix identifying where the code lives.

Additionally, take the opportunity to fix up two API mistakes: emit_reloc's
arguments were in a nonsensical order, and set_tiling lacked the stride
argument that the kernel will want to use soon.  API compatibility with
released code is maintained using #defines.