main: add binary support to GetProgramBinary

V2: call generic _mesa_get_program_binary() helper rather than driver
    function directly to allow greater code sharing.

Signed-off-by: Timothy Arceri <tarceri@itsqueeze.com>
Signed-off-by: Jordan Justen <jordan.l.justen@intel.com> (v1)
Reviewed-by: Nicolai Hähnle <nicolai.haehnle@amd.com> (v1)
Reviewed-by: Tapani Pälli <tapani.palli@intel.com>

src/mesa/main/shaderapi.c

@@ -2199,12 +2199,15 @@ _mesa_GetProgramBinary(GLuint program, GLsizei bufSize, GLsizei *length,
       return;
    }
 
+   if (ctx->Const.NumProgramBinaryFormats == 0) {
       *length = 0;
       _mesa_error(ctx, GL_INVALID_OPERATION,
                   "glGetProgramBinary(driver supports zero binary formats)");
-
-   (void) binaryFormat;
-   (void) binary;
+   } else {
+      _mesa_get_program_binary(ctx, shProg, bufSize, length, binaryFormat,
+                               binary);
+      assert(*length == 0 || *binaryFormat == GL_PROGRAM_BINARY_FORMAT_MESA);
+   }
 }
 
 void GLAPIENTRY