cap: remove logging code (moved to ~/bin/imgur)

Let's do it in the proper place...
lib.bash: set defaults for XDG variables

Do not export to environment, just set for the script itself.
allow input text to be given in command line
fix whitespace
do not lose truncated escape at EOF
warn about truncated hex escapes

No "quiet" option; /dev/null it if you want.
warn about unknown escapes

Unsure about this one, but, again, /dev/null works
show file name in warnings
keep track of current position manually

ftell() does not work on pipes like stdin.
do not increment pos at EOF
so I ended up implementing --quiet

Redirecting stderr to /dev/null might hide fopen() errors.
Merge /home/grawity/projects/unescape