mesalib: Update version from 18.3.3 to 18.3.4

From the [announcement][1]:

> Mesa 18.3.4 is now available.
>
> In this release we have:
>
> A fix in the XvMC state-tracker, which was causing some video attributes to
> not take affect. On the video front the VAAPI state tracker has seen
> improvements with VP9 streams while the amdgpu driver advertises all available
> profiles.
>
> On Intel side we have compiler fixes and extra PCI IDs for Coffee Lake and
> Ice Lake parts. In the Broadcom drivers a couple of memory leaks were
> addressed and the NEON assembly should compile properly on armhf.
>
> Other drivers such as radeonsi, nouveau and freedreno have also seen some
> love. The RADV driver has seen addressed to compile correctly with GCC9
> amongst other changes.
>
> The Xlib based libGL have been addressed to work with X servers, which lacks
> the MIT-SHM extension such as XMing.
>
> To top it up we have a few fixes to the meson build system.

[1]: https://lists.freedesktop.org/archives/mesa-dev/2019-February/215484.html

mesalib.be0

@@ -1,6 +1,6 @@
 #!/usr/bin/env beesh
 
-# BEE_VERSION mesalib-18.3.3-0
+# BEE_VERSION mesalib-18.3.4-0
 
 ## this file was created by bee init and should be executed to build a
 ## bee-package. (Additional hints are located at the end of this file.)