Replace the XDummy script with Xephyr. This is done because of some
changes in the Xorg server that make XDummy difficult to use.
Rename library internal variables and function names to replace "xdummy"
with "xserver" to show this change (except for renaming the package and
lib file for better git history).
Rename the switch `--keep-xdummy-output` to `--keep-xserver-output`.
This switch should now be rarely used because Xephyr requires less set
up.
Replace "xdummy" with "xephyr" in comments and utility help
information. Update docs to show the new dependency.
fixes#1367
Adds two files to gitignore.
`.clang_complete` is created by the clang_complete vim plugin
[https://github.com/Rip-Rip/clang_complete]
`Xdummy.so` is created by compiling the Xdummy module.
This patch splits the main .gitignore with a specific
testcases/.gitignore and also add 4 patterns to the ignore list:
i3-command-parser.stamp
i3-config-parser.stamp
testcases/-
testcases/i3-cfg-for-*
