Fix timezone management in the C library

Define 'timezone' and 'daylight' global variables that are already
defined in <time.h>

Properly update the 'tm_gmtoff' field in 'struct tm' values.

libc/Android.mk

@@ -408,6 +408,14 @@ libc_common_cflags := \
 		-DUSE_DL_PREFIX \
 		-DPOSIX_MISTAKE
 
+# these macro definitions are required to implement the
+# 'timezone' and 'daylight' global variables, as well as
+# properly update the 'tm_gmtoff' field in 'struct tm'.
+#
+libc_common_cflags += \
+    -DTM_GMTOFF=tm_gmtoff \
+    -DUSG_COMPAT=1
+
 ifeq ($(strip $(DEBUG_BIONIC_LIBC)),true)
   libc_common_cflags += -DDEBUG
 endif

libc/docs/CHANGES.TXT

@@ -70,6 +70,12 @@ Differences between current and Android 2.1:
 
 - add sigaltstack() implementation for ARM.
 
+- <time.h>: Properly implement the 'timezone' and 'daylight' global variables
+  (they were not defined previously, though declared in the header).
+
+- <time.h>: Fix timezone management implementation to properly update
+  'tm_gmtoff' field in 'struct tm' structure.
+
 -------------------------------------------------------------------------------
 Differences between Android 2.1 and 2.0.1: