Switch to Vista instead of Win2K.

Bug: http://b/26524325
Bug: http://b/25282907

The latest Clang/LLVM requires Vista APIs in order to execute, so we
need to bump the minimum required Windows version for our host tools.

Change-Id: Ic1a760bc240060f5de39ce3a68484886021ff3d9
diff --git a/core/combo/HOST_CROSS_windows-x86.mk b/core/combo/HOST_CROSS_windows-x86.mk
index 1ac1059..b6cbebc 100644
--- a/core/combo/HOST_CROSS_windows-x86.mk
+++ b/core/combo/HOST_CROSS_windows-x86.mk
@@ -32,8 +32,8 @@
 $(combo_var_prefix)GLOBAL_CFLAGS += -D__STDC_FORMAT_MACROS -D__STDC_CONSTANT_MACROS
 # Use C99-compliant printf functions (%zd).
 $(combo_var_prefix)GLOBAL_CFLAGS += -D__USE_MINGW_ANSI_STDIO=1
-# Admit to using >= Win2K. Both are needed because of <_mingw.h>.
-$(combo_var_prefix)GLOBAL_CFLAGS += -D_WIN32_WINNT=0x0500 -DWINVER=0x0500
+# Admit to using >= Vista. Both are needed because of <_mingw.h>.
+$(combo_var_prefix)GLOBAL_CFLAGS += -D_WIN32_WINNT=0x0600 -DWINVER=0x0600
 # Get 64-bit off_t and related functions.
 $(combo_var_prefix)GLOBAL_CFLAGS += -D_FILE_OFFSET_BITS=64