Added workaround for broken X login on Debian 6.

This (default?) Debian 6.0 box has /bin/sh -> /bin/dash. X
Display Manager runs "/bin/sh /etc/gdm3/Xsession default". This
Xsession script has shebang /bin/sh and sources ~/.profile,
thus .profile is invoked with wrong shell, which even is not an
interactive shell! IMHO this is really sick, no clue why they did
it. Also there sis /bin/sh -> /bin/dash, but SHELL=/bin/bash in
Xsession!

There are several related bug reports, but most proposed
workarounds did not work. For example, "shopts -o posix" and
"if [[ $- != *i* ]] ; then return ; fi" do not work in dash.

I thought Xsession sources ~/.profile as a dirty hack to get
users PATH and friends even if they are set in the wrong place to
make ALT-F2 in meta-city able to execute scripts from ~/bin, but
this does not work at all...
Deprecated .bashrc-ssh: sources .bashrc.
git-quickdox.txt: Remote tags by default.
vimrc: middle mouse as independent buffer.
bin/gdb: search in ~steffen/usr/bin first.

Needed when invoked by other user who has no ~steffen/usr/bin in PATH,
but of course wants same environment.
.vimrc: new nd-style.
.vimrc: allow utf8 if available.
.vimrc: Consolas font if available.
.vimrc: fun LargerFont().
.vimrc: fun LargerFont() sets all fonts.
.vimrc: ",+": font++, no colorcolumn.

Colorcolumn seems not to work fully correctly (VIM-7.3), when
switching buffers or I'm using it wrongly, so better disable it
for now, maybe future VIMs handle it better.
git-quickdox.txt: git-svn and "file-based history".
vimrc: overlength darkblue.
git-quickdox.txt: SVN cookbook.