patch 7.4.756
Problem:    Can't use strawberry Perl 5.22 x64 on MS-Windows.
Solution:   Add new defines and #if. (Ken Takata)
diff --git a/src/Make_mvc.mak b/src/Make_mvc.mak
index 063282d..a6534c8 100644
--- a/src/Make_mvc.mak
+++ b/src/Make_mvc.mak
@@ -874,7 +874,7 @@
 !endif
 !endif
 
-CFLAGS = $(CFLAGS) -DFEAT_PERL
+CFLAGS = $(CFLAGS) -DFEAT_PERL -DPERL_IMPLICIT_CONTEXT -DPERL_IMPLICIT_SYS
 
 # Do we want to load Perl dynamically?
 !if "$(DYNAMIC_PERL)" == "yes"