Fix ICU time zone support on iOS

patches/ios_timezone.patch

+--- public/common/unicode/pmac.h
++++ public/common/unicode/pmac.h
+@@ -50,6 +50,16 @@
+ #endif
+ 
+ #include <AvailabilityMacros.h>
++#include <TargetConditionals.h>
++
++/**
++ * Add a second platform define to handle differences between Mac OS X and iOS
++ */
++#if TARGET_OS_IPHONE
++#ifndef U_IOS
++#define U_IOS
++#endif
++#endif
+ 
+ /**
+  * \def U_HAVE_DIRENT_H
+@@ -288,11 +299,16 @@
+ #if 1
+ #define U_TZSET         tzset
+ #endif
++#ifndef U_IOS
++/* The iOS version of timezone is busted (at least in the simulator, it is
++   never set to anything useful). Leave it undefined to avoid a code path
++   in putil.c. */
+ #if MAC_OS_X_VERSION_MIN_REQUIRED < MAC_OS_X_VERSION_10_5
+ #define U_TIMEZONE 0
+ #else
+ #define U_TIMEZONE timezone
+ #endif
++#endif  // !U_IOS
+ #if 1
+ #define U_TZNAME        tzname
+ #endif
+--- source/common/putil.c
++++ source/common/putil.c
+@@ -623,20 +623,28 @@ uprv_timezone()
+ #else
+     time_t t, t1, t2;
+     struct tm tmrec;
++#ifndef U_IOS
+     UBool dst_checked;
++#endif
+     int32_t tdiff = 0;
+ 
+     time(&t);
+     uprv_memcpy( &tmrec, localtime(&t), sizeof(tmrec) );
++#ifndef U_IOS
+     dst_checked = (tmrec.tm_isdst != 0); /* daylight savings time is checked*/
++#endif
+     t1 = mktime(&tmrec);                 /* local time in seconds*/
+     uprv_memcpy( &tmrec, gmtime(&t), sizeof(tmrec) );
+     t2 = mktime(&tmrec);                 /* GMT (or UTC) in seconds*/
+     tdiff = t2 - t1;
++#ifndef U_IOS
++    /* On iOS the calculated tdiff is correct so and doesn't need this dst
++       shift applied. */
+     /* imitate NT behaviour, which returns same timezone offset to GMT for
+        winter and summer*/
+     if (dst_checked)
+         tdiff += 3600;
++#endif
+     return tdiff;
+ #endif
+ }
+@@ -649,7 +661,7 @@ uprv_timezone()
+ extern U_IMPORT char *U_TZNAME[];
+ #endif
+ 
+-#if !UCONFIG_NO_FILE_IO && (defined(U_DARWIN) || defined(U_LINUX) || defined(U_BSD))
++#if !UCONFIG_NO_FILE_IO && ((defined(U_DARWIN) && !defined(U_IOS)) || defined(U_LINUX) || defined(U_BSD))
+ /* These platforms are likely to use Olson timezone IDs. */
+ #define CHECK_LOCALTIME_LINK 1
+ #if defined(U_DARWIN)