mingw32-git: Fix the default http.sslCAInfo path

Signed-off-by: Sebastian Schuberth <sschuberth@gmail.com>
readme: Note that cloning via the installer will automatically set the filters

Signed-off-by: Sebastian Schuberth <sschuberth@gmail.com>
mingw32-git: Use mingw-get post-install actions defined as Lua in the XML

Use the Lua-based post-install actions as provided by mingw-get instead of
the shell-based approach that mgwport is supposed to provide (but that does
not work yet).

Signed-off-by: Sebastian Schuberth <sschuberth@gmail.com>