Add /etc/profile and /etc/inputrc for easier customization

These are the original versions from msys-core-1.0.18.

Signed-off-by: Karsten Blees <blees@dcon.de>
/etc/profile: use /etc/inputrc if ~/.inputrc doesn't exist

The MSYS /etc/profile script copies a default inputrc file into the user's
HOME directory and ignores /etc/inputrc completely.

The average Windows user won't know about inputc anyway, so there's no
point creating personal copies. And users that _do_ know will expect it to
behave as documented [1].

Fix it to use ~/.inputrc if it exists, otherwise fall back to /etc/inputrc.

[1] https://www.gnu.org/software/bash/manual/html_node/Readline-Init-File.html

Signed-off-by: Karsten Blees <blees@dcon.de>
/etc/inputrc: enable Unicode console input

Note: this requires Unicode-enabled msys-core and bash to work.

Signed-off-by: Karsten Blees <blees@dcon.de>
/etc/profile: set HOME to the user's home or profile directory

The MSYS profile script tries to create "/home/$LOGNAME" if HOME is not
set. However, on Windows, a normal user cannot create files or directories
in the installation directory.

Set the HOME variable to $HOMEDRIVE$HOMEPATH if it exists and is a
directory, otherwise to $USERPROFILE. This is how current Git for Windows
shells, TortoiseGit and GitExtensions do it as well.

Picked from msysgit, but dropped the warning line about msysGit issue 108.
The old Goole issue tracker has been deleted, and the issue is fixed by
msys-core patch "msys.dll: basic Unicode support".

Finally, remove the same now redundant logic from "Git Bash.vbs".

Signed-off-by: Karsten Blees <blees@dcon.de>
Signed-off-by: Sebastian Schuberth <sschuberth@gmail.com>
/etc/profile: start in the current working directory

Do not change the current directory when starting a shell.

Signed-off-by: Karsten Blees <blees@dcon.de>
Signed-off-by: Sebastian Schuberth <sschuberth@gmail.com>