Converted the Makefile functionality into several bat files to better
support building on Windows. All targets have been introduced in the
make.bat file, except for "cov" and "format".
Running make.bat with no arguments runs the all target per default,
just like Makefile.
If an argument is supplied, it must be one of all, cover, deps,
integ, test, vet, or updatedeps.
For example
> make.bat test
runs the test target.
