meson: Build i965 and dri stack

meson: Build i965 and dri stack

This gets pretty much the entire classic tree building, as well as
i965, including the various glapis. There are some workarounds for bugs
that are fixed in meson 0.43.0, which is due out on October 8th.

I have tested this with piglit using glx.

v2: - fix typo "vaule" -> "value"
    - use gtest dep instead of linking to libgtest (rebase error)
    - use gtest dep instead of linking against libgtest (rebase error)
    - copy the megadriver, then create hard links from that, then delete
      the megadriver. This matches the behavior of the autotools build.
      (Eric A)
    - Use host_machine instead of target_machine (Eric A)
    - Put a comment in the right place (Eric A)
    - Don't have two variables for the same information (Eric A)
    - Put pre_args at top of file in this patch (Eric A)
    - Fix glx generators in this patch instead of next (Eric A)
    - Remove -DMESON hack (Eric A)
    - add sha1_h to mesa in this patch (Eric A)
    - Put generators in loops when possible to reduce code in
      mapi/glapi/gen (Eric A)
v3: - put HAVE_X11_PLATFORM in this patch

Signed-off-by: Dylan Baker <dylanx.c.baker@intel.com>
Reviewed-by: Eric Anholt <eric@anholt.net>