Fixing conflict with SDK off_t definition.

src/os/win32/ngx_win32_config.h

diff --git a/src/os/win32/ngx_win32_config.h b/src/os/win32/ngx_win32_config.h
index cc4c375..8ffe95c 100644
--- a/src/os/win32/ngx_win32_config.h
+++ b/src/os/win32/ngx_win32_config.h
@@ -126,8 +126,11 @@
 typedef int                 intptr_t;
 typedef u_int               uintptr_t;
 
-typedef int                 ssize_t;
+/* Windows defines off_t as long, which is 32-bit */
 typedef __int64             off_t;
+#define _OFF_T_DEFINED
+
+typedef int                 ssize_t;
 typedef uint32_t            in_addr_t;
 typedef u_short             in_port_t;
 typedef int                 sig_atomic_t;