xrdp: Fix format string vulnerability

The the string being printer contains a "%", this could crash xrdp.
doc: Format manual page references

Use .BR to fromat name(section) as recommended by man(7).
X11rdp: Remove duplicate entry for expat

expat-2.0.1.tar.gz is declared twice, remove the first one.
X11rdp: Consistently use $file

Consistently use $file instead of repeating the file name again when
downloading external URLs.
X11rdp: fix indention

Re-indent four sections to use 4 spaces for indention
X11rdp: simplify download

Use case-statement instead of many ifs.
X11rdp: simplify line splitting

Use "IFS=: read" instead of "echo|cut" constructs.
X11rdp: Simplify if constructs

Directly use exit value instead of evaluating $?
X11rdp: Handle more compression formats

Add .xz and plain .tar files.
X11rdp: fix spelling mistages

exit -> exist
$mn -> $mod_name
X11rdp: make variables function local

Use local to declare variables local
X11rdp: Rework changing directories

Remove unchecked changes of directories.