_mesa_meta_GenerateMipmap: Support all texture targets by generating shaders at runtime

_mesa_meta_GenerateMipmap: Support all texture targets by generating shaders at runtime

This is a squash for the following 7 commits.  The first introduces the
functionality, and the remaining six fix various bugs.

Patch 1:
    _mesa_meta_GenerateMipmap: Support all texture targets by generating shaders at runtime

    glsl path of _mesa_meta_GenerateMipmap() function would require different fragment
    shaders depending on the texture target. This patch adds the code to generate
    appropriate fragment shader programs at run time.
    Fixes https://bugs.freedesktop.org/show_bug.cgi?id=54296

    V2: Removed the code for integer textures as ARB is planning to
        disallow automatic mipmap generation for integer textures.
        Now using ralloc_asprintf in setup_glsl_generate_mipmap().

    NOTE: This is a candidate for stable branches.

    Signed-off-by: Anuj Phogat <anuj.phogat@gmail.com>
    Reviewed-by: Brian Paul <brianp@vmware.com>
    (cherry picked from commit 299acac849eb8506de9760c94c6e8e8b1046d909)

Patch 2:
    _mesa_meta_GenerateMipmap: Generate separate shaders for glsl 120 / 130

    glsl version of _mesa_meta_GenerateMipmap() would require separate
    shaders for glsl 120 and 130.

    V2: Removed the code for integer textures as ARB is planning to
        disallow automatic mipmap generation for integer textures.

    NOTE: This is a candidate for stable branches.

    Signed-off-by: Anuj Phogat <anuj.phogat@gmail.com>
    Reviewed-by: Brian Paul <brianp@vmware.com>
    (cherry picked from commit 15bf3103b48a5928321fe56fbb3ed28a0f314418)

Patch 3:
    meta: Add on demand compilation of per target shader programs

    A call to glGenerateMipmap() follows the generation of a relevant
    shader program in setup_glsl_generate_mipmap().

    To support all texture targets and to avoid compiling shaders
    everytime, per target shader programs are compiled on demand
    and saved for the next call.

    Fixes float-texture(mipmap.manual):
    See Comment 6: https://bugs.freedesktop.org/show_bug.cgi?id=54296

    NOTE: This is a candidate for stable branches.

    Signed-off-by: Anuj Phogat <anuj.phogat@gmail.com>
    Reviewed-by: Brian Paul <brianp@vmware.com>
    (cherry picked from commit eb1d87fb945783448cc40ad43c9cd4d98002d424)

Patch 4:
    meta: make mem_ctx non-global.

    I can't see any external users, and this is a global symbol,

    Reviewed-by: Matt Turner <mattst88@gmail.com>
    Signed-off-by: Dave Airlie <airlied@redhat.com>
    (cherry picked from commit 36639ec6e9a2758e344235fbdc1450719d8851e3)

Patch 5:
    meta: Remove unsafe global mem_ctx pointer

    NOTE: This is a candidate for the 9.0 branch.

    Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
    Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
    Reviewed-by: Brian Paul <brianp@vmware.com>
    Reviewed-by: Anuj Phogat <anuj.phogat@gmail.com>
    (cherry picked from commit ab097dde0c958dd8b1c06a07ef8913512753760c)

Patch 6:
    meta: Rearrange shader creation in setup_glsl_generate_mipmap

    The diff looks weird, but this moves the code from the first 'if
    (ctx->Const.GLSLVersion < 130)' block down into the second block.  It
    also moves some variable decalarations closer to their use.

    NOTE: This is a candidate for the 9.0 branch.

    Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
    Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
    Reviewed-by: Brian Paul <brianp@vmware.com>
    Reviewed-by: Anuj Phogat <anuj.phogat@gmail.com>
    (cherry picked from commit 3308c079bd00e9b9aa546f5214ce197a904d059b)

Patch 7:
    meta: Don't use GLSL 1.30 shader on OpenGL ES 2

    Fixes GLES2 CoverageGL conformance test.

    NOTE: This is a candidate for the 9.0 branch.

    Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
    Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
    Reviewed-by: Brian Paul <brianp@vmware.com>
    Reviewed-by: Anuj Phogat <anuj.phogat@gmail.com>
    (cherry picked from commit 0242381f06edb09dcf0eaacd6d26ccd8584700cc)