patch 9.1.0616: filetype: Make syntax highlighting off for MS Makefiles

patch 9.1.0616: filetype: Make syntax highlighting off for MS Makefiles

Problem:  filetype: Make syntax highlighting off for MS Makefiles
Solution: Try to detect MS Makefiles and adjust syntax rules to it.
          (Ken Takata)

Highlighting of variable expansion in Microsoft Makefile can be broken.
E.g.:
https://github.com/vim/vim/blob/2979cfc2627d76a9c09cad46a1647dcd4aa73f5f/src/Make_mvc.mak#L1331

Don't use backslash as escape characters if `make_microsoft` is set.
Also fix that `make_no_comments` was not considered if `make_microsoft`
was set.

Also add description for `make_microsoft` and `make_no_comments` to the
documentation and include a very simple filetype test

closes: #15341

Signed-off-by: Christian Brabandt <cb@256bit.org>
Signed-off-by: Ken Takata <kentkt@csc.jp>