Starting with bash-completion 1.90 (released in November 2011) completion files should be installed in the share/ directory.
They must use the executable’s name for loading on demand, so for this reason, it was necessary to generate the completion file in a new directory, so that it does not clash with the `youtube-dl` executable.
This is because Python’s setup-tools does not support data files to be installed with a different base name.
I have tested this change with both `make install` and `pip install`, as these two install procedures have slightly different code paths.
I removed the `bash-completion` (phony) target from the make file, as we now have a directory with that name, and I could not see the target being referenced anywhere.
Closes#804.
7a4e8d91d2