mesa-demos: Add version 8.3.0

Description [1]:

> The Mesa Demos package contains a large number of OpenGL demonstration
> and test programs.
>
> These programs were previously distributed as the MesaDemos-x.y.z.tar.gz
> package released in conjunction with the MesaLib-x.y.z.tar.gz package.
> The demos are separated now since they don't change often and
> aren't tied to a particular version of Mesa.
>
> Note that the Mesa demos should be usable with any OpenGL
> implementation; not just Mesa.

Version 8.3.0 was released on December 9th, 2015.

Instead of patching the Mesa 3D source code as documented in the BLFS
book [2], build a separate package for the Mesa 3D demo programs.

Create the versionless bee file with the commands below.

```
$ bee init https://mesa.freedesktop.org/archive/demos/8.3.0/mesa-demos-8.3.0.tar.bz2
creating mesa-demos-8.3.0-0.bee from template '/etc/default/bee/templates/fallback'
$ git add mesa-demos-8.3.0-0.bee
$ git mv mesa-demos-8.3.0-0.bee mesa-demos.bee
$ vim mesa-demos.bee
$ git add $_
```

[1] https://cgit.freedesktop.org/mesa/demos/tree/index.html
[2] http://www.linuxfromscratch.org/blfs/view/svn/x/mesa.html

mesa-demos.be0

@@ -0,0 +1,85 @@
+#!/usr/bin/env beesh
+
+# BEE_VERSION mesa-demos-8.3.0-0
+
+## 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.)
+
+###############################################################################
+## The source URL(s) define the location of the sources that will be
+## downloaded. Version variables may be used to simplify reuse of this bee-file.
+
+SRCURL[0]="https://mesa.freedesktop.org/archive/demos/${PKGVERSION}/mesa-demos-${PKGVERSION}.tar.bz2"
+
+###############################################################################
+## Add URLs/pathes to patch files to the PATCHURL array.
+## The sources will be patched in the order of the array.
+
+# PATCHURL+=()
+
+###############################################################################
+## Add filename patterns to the EXCLUDE array of files that should not
+## be added to you package but may be present in the image directory.
+
+# EXCLUDE+=()
+
+###############################################################################
+## Uncomment the next statement, if the software may not be able to be built
+## outside the source directory and needs to be built inside the source
+## directory.
+
+# build_in_sourcedir
+
+###############################################################################
+## bee cannot detect buildtypes specified in subdirectories.
+## Sometimes packages "hide" the real sources in a subdirectory named
+## 'src' or 'cmake' or ..
+## use 'sourcesubdir_append' to specify this directory if known.
+
+# sourcesubdir_append src
+
+
+###############################################################################
+## Change the default (auto-detected) steps to
+## extract, patch, configure/setup, build and install the software.
+## Make sure the mee_install function does install everything to the
+## image directory "${D}"
+
+#mee_extract() {
+#    bee_extract "${@}"
+#}
+
+#mee_patch() {
+#    bee_patch "${@}"
+#}
+
+#mee_configure() {
+#    bee_configure
+#}
+
+#mee_build() {
+#    bee_build
+#}
+
+#mee_install() {
+#    bee_install
+#}
+## by default this may be 'make install DESTDIR="${D}"'
+
+###############################################################################
+##
+## Additional hints:
+##
+## The name of this bee-file should follow the following naming convention:
+##     pkgname-pkgversion-pkgrevision.bee
+##
+## You may remove all comments as long as SRCURL[0] is set.
+##
+## Everything in this file will be executed in a bash environment.
+##
+## Build the package by executing
+##     './pkg-version-N.bee' or
+##     'beesh ./pkg-version-N.bee'
+##
+## see http://beezinga.org/
+##