Enable _XOPEN_SOURCE=700 on cygwin to get the wcwidth function

src/Makefile

@@ -50,6 +50,7 @@ else ifeq ($(os),DragonFly)
     CPPFLAGS += -I/usr/local/include
     LDFLAGS += -L/usr/local/lib
 else ifneq (,$(findstring CYGWIN,$(os)))
+    CXXFLAGS += -D_XOPEN_SOURCE=700
     LIBS += -lncursesw -lboost_regex -ldbghelp
 else
     LIBS += -lncursesw -lboost_regex

src/unicode.hh

@@ -2,6 +2,7 @@
 #define unicode_hh_INCLUDED
 
 #include <wctype.h>
+#include <wchar.h>
 #include <locale>
 
 namespace Kakoune