glsl: Linker support for ARB_shader_atomic_counters.

glsl: Linker support for ARB_shader_atomic_counters.

v2: Add comments on the purpose of the auxiliary data structures.
    Check for atomic counter overlaps.  Use the contains_atomic()
    convenience method.  Add static assert with the number of expected
    shader stages.
v3: Don't resize atomic arrays.
v4: Add comment on the reason why we don't resize atomic counter
    arrays.  Use 'strcmp(...) == 0' instead of '!strcmp(...)'.
v5 (idr):  Don't use STL in the linker.

Signed-off-by: Francisco Jerez <currojerez@riseup.net>
Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>