mesa cleanup: remove patches, clean description

werror-wundef.patch came from #1082, but now no longer applied,
and it seems no longer necessary, as both qt5 and qtCreator build.
@bbenoist: was the patch useful for anything else?

pkgs/development/libraries/mesa/default.nix

@@ -12,14 +12,14 @@ else
 
 /** Packaging design:
   - The basic mesa ($out) contains headers and libraries (GLU is in mesa_glu now).
-    This or the mesa attribute (which also contains GLU) are small (~ 2.2 MB, mostly headers)
+    This or the mesa attribute (which also contains GLU) are small (~ 2 MB, mostly headers)
     and are designed to be the buildInput of other packages.
   - DRI and EGL drivers are compiled into $drivers output,
-    which is bigger (~13 MB) and depends on LLVM (~44 MB).
+    which is much bigger and depends on LLVM.
     These should be searched at runtime in "/run/opengl-driver{,-32}/lib/*"
     and so are kind-of impure (given by NixOS).
     (I suppose on non-NixOS one would create the appropriate symlinks from there.)
-  - libOSMesa is in $osmesa (~4.2 MB)
+  - libOSMesa is in $osmesa (~4 MB)
 */
 
 let
@@ -39,10 +39,10 @@ stdenv.mkDerivation {
 
   prePatch = "patchShebangs .";
 
-  patches = [ # some don't apply -- try without them ATM
+  patches = [
     ./static-gallium.patch
-   # ./dricore-gallium.patch
-   # ./werror-wundef.patch
+   # TODO: revive ./dricore-gallium.patch when it gets ported (from Ubuntu),
+   #  as it saved ~35 MB in $drivers; watch https://launchpad.net/ubuntu/+source/mesa/+changelog
   ];
 
   # Change the search path for EGL drivers from $drivers/* to driverLink