[PATCH] add NO_PERL_XS for environments which are not able to support perl extensions

At the moment, the only known example of such environment is Cygwin with
ActiveState Perl: Makefile, generated by the MakeMaker from ActiveState perl
distribution is not usable by cygwin's gmake.

Signed-off-by: Alex Riesen <redacted>
---
 Makefile |   39 +++++++++++++++++++++++++++++++++------
 1 files changed, 33 insertions(+), 6 deletions(-)