driconf: add force_glsl_abs_sqrt option

This will allow to force computing the absolute value for sqrt()
and inversesqrt() in order to follow D3D9 behaviour for buggy
apps that rely on it.

Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>

src/gallium/include/state_tracker/st_api.h

@@ -248,6 +248,7 @@ struct st_config_options
    boolean allow_glsl_extension_directive_midshader;
    boolean allow_higher_compat_version;
    boolean glsl_zero_init;
+   boolean force_glsl_abs_sqrt;
    unsigned char config_options_sha1[20];
 };