genxml: New generated header genX_bits.h (v6)

genxml: New generated header genX_bits.h (v6)

genX_bits.h contains the sizes of bitfields in genxml instructions,
structures, and registers. It also defines some functions to query those
sizes.

isl_surf_init() will use the new header to validate that requested
pitches fit in their destination bitfields.

What's currently in genX_bits.h:

  - Each CONTAINER::Field from gen*.xml that has a bitsize has a macro
    in genX_bits.h:

        #define GEN{N}_CONTAINER_Field_bits {bitsize}

  - For each set of macros whose name, after stripping the GEN prefix,
    is the same, genX_bits.h contains a query function:

      static inline uint32_t __attribute__((pure))
      CONTAINER_Field_bits(const struct gen_device_info *devinfo);

v2 (Chad Versace):
  - Parse the XML instead of scraping the generated gen*_pack.h headers.

v3 (Dylan Baker):
  - Port to Mako.

v4 (Jason Ekstrand):
  - Make the _bits functions take a gen_device_info.

v5 (Chad Versace):
  - Fix autotools out-of-tree build.
  - Fix Android build. Tested with git://github.com/android-ia/manifest.
  - Fix macro names. They were all missing the "_bits" suffix.
  - Fix macros names more. Remove all double-underscores.
  - Unindent all generated code. (It was floating in a sea of whitespace).
  - Reformat header to appear human-written not machine-generated.
  - Sort gens from high to low. Newest gens should come first because,
    when we read code, we likely want to read the gen8/9 code and ignore
    the gen4 code. So put the gen4 code at the bottom.
  - Replace 'const' attributes with 'pure', because the functions now
    have a pointer parameter.
  - Add --cpp-guard flag. Used by Android.
  - Kill class FieldCollection. After Jason's rewrite, it was just
    a dict.

v6 (Chad Versace):
  - Replace `key not in d.keys()` with `key not in d`. [for dylan]

Co-authored-by: Dylan Baker <dylan@pnwbakers.com>
Co-authored-by: Jason Ekstrand <jason@jlekstrand.net>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net> (v5)
Reviewed-by: Dylan Baker <dylan@pnwbakers.com> (v6)