mesa: reduce the size of gl_viewport_attrib

All drivers convert these to float, so there is no reason to use double.
The piglit test that expects double precision from glGet will be adjusted
not to require it (there is a piglit patch).

gl_context::ViewportArray: 512 -> 384 bytes

Reviewed-by: Mathias Fröhlich <mathias.froehlich@web.de>
Reviewed-by: Brian Paul <brianp@vmware.com>

src/mesa/drivers/common/meta.h

@@ -158,7 +158,7 @@ struct save_state
 
    /** MESA_META_VIEWPORT */
    GLfloat ViewportX, ViewportY, ViewportW, ViewportH;
-   GLclampd DepthNear, DepthFar;
+   GLclampf DepthNear, DepthFar;
 
    /** MESA_META_CLAMP_FRAGMENT_COLOR */
    GLenum ClampFragmentColor;

src/mesa/main/mtypes.h

@@ -1407,7 +1407,7 @@ struct gl_viewport_attrib
 {
    GLfloat X, Y;		/**< position */
    GLfloat Width, Height;	/**< size */
-   GLdouble Near, Far;		/**< Depth buffer range */
+   GLfloat Near, Far;		/**< Depth buffer range */
 };