.shell/aliases: use /usr/bin/grep too for lgrep alias

Signed-off-by: Nicolas Iooss <nicolas.iooss_git@polytechnique.org>
.shell/aliases: add mailq-hold alias

Signed-off-by: Nicolas Iooss <nicolas.iooss_git@polytechnique.org>
.shell/aliases: add gitka alias

Signed-off-by: Nicolas Iooss <nicolas.iooss_git@polytechnique.org>