Fix: build: Adapt man page generation for glib.

help2man and the glib command line processing code do not really fit
together well. In order to continue generating useful man pages, several
things have to be done here:

• The if block in Makefile.common is to support both tools that use glib

and tools that are still using our own command line code.

• help2man needs to be told to use --help-all.

• The new included file does three things. One, it adds a synopsis

section to the man page. Two, it adds an OPTIONS header after the
description so all the options do not appear listed there. Three, it
makes sure the tool name does not start with lt- due to libtool being
run during the build process.

• The sed command removes a redundant and bad looking usage block from

the description.