Don't use strptime() in Cygwin

There's a compile warning of strptime() not being declared.  It should be
declared by <time.h> but is maybe missing a macro.  There are apparently
some limitations in strptime() too, so disable its use for now, as local
time parsing is not a mandatory feature.

src/duk_features.h.in

@@ -177,12 +177,17 @@ static __inline__ unsigned long long duk_rdtsc(void) {
 #define DUK_F_BSD
 #endif
 
-/* Generic Unix */
+/* Generic Unix (includes Cygwin) */
 #if defined(__unix) || defined(__unix__) || defined(unix) || \
     defined(DUK_F_LINUX) || defined(DUK_F_BSD)
 #define DUK_F_UNIX
 #endif
 
+/* Cygwin */
+#if defined(__CYGWIN__)
+#define DUK_F_CYGWIN
+#endif
+
 /* Windows (32-bit or above) */
 #if defined(_WIN32) || defined(WIN32) || defined(_WIN64) || defined(WIN64) || \
     defined(__WIN32__) || defined(__TOS_WIN__) || defined(__WINDOWS__)
@@ -482,6 +487,17 @@ static __inline__ unsigned long long duk_rdtsc(void) {
 #include <sys/param.h>
 #include <sys/time.h>
 #include <time.h>
+#elif defined(DUK_F_CYGWIN)
+/* Cygwin -- don't use strptime() for now */
+#define DUK_USE_DATE_NOW_GETTIMEOFDAY
+#define DUK_USE_DATE_TZO_GMTIME_R
+#define DUK_USE_DATE_FMT_STRFTIME
+#include <sys/types.h>
+#include <endian.h>
+#include <limits.h>
+#include <sys/param.h>
+#include <sys/time.h>
+#include <time.h>
 #else
 /* Other UNIX, hopefully others */
 #define DUK_USE_DATE_NOW_GETTIMEOFDAY