This fixes completing filenames containing single quote (') on bash-4.
Also added emulation of `-o filenames' to _filedir.
Added tests for _filedir.
Fixed array assignment within __reassemble_comp_words_by_ref().
Code in `unit_start()' and `completion_start()' is merged and put central in
lib/library.exp:
- start_bash()
- source_bash_completion()
- init_tcl_bash_globals()
Global string variable `bash_versinfo_0' is replaced with list variable
`BASH_VERSINFO'.
Completing directories after `screen -c' passes on bash-4 now that
_filedir does a `compopt -o filenames'.
The test yields an expected failure on bash-3.
