ensure that under MS Windows standard cmd shell executes bang commands

all of the latexmk and util library assumes that
under MS Windows the cmd shell is used.

The commit does this assumption justice.
Merge pull request #85 from Konfekt/master

ensure that under MS Windows cmd shell executes bang commands
Break long lines
ensure that under MS Windows standard cmd shell executes bang commands

all of the latexmk and util library assumes that
under MS Windows the cmd shell is used.

The commit does this assumption justice.