buildscripts: Integrate install prefix.

And change directory structure.
Convert git related alias to respective scripts.

This allows the commands to be used in shell script.
Add script to symlink all files.
dotfiles/.hgrc: Add extension 'purge'
Update ln.sh
Add several forgotten patches.
Move several files' path to /tmp.
ln.sh: Don't symlink autorebase.bat but copy it
Add dotfiles/{.bash_logout, .tigrc}.
mintty_exp.bat: Fix failed login attempt.
dotfiles/.bashrc: Add more alias
mpfr: Update patch level to p10.
buildscripts/flac.sh: Fix typo.
Move scripts under /usr/bin to /usr/local/bin
cpath: Don't put CMD_PATH to PATH in the case of nogcc.