Win32: disabled MSVC warning about '\0' not fitting into array.

We believe that this warning produces more inconvience than real benefit.
Here is an example to trigger:

  u_char a[4] = "test";

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 1ebbf86..3f3b3e3 100644
--- a/src/os/win32/ngx_win32_config.h
+++ b/src/os/win32/ngx_win32_config.h
@@ -70,6 +70,9 @@
 /* FD_SET() and FD_CLR(): conditional expression is constant */
 #pragma warning(disable:4127)
 
+/* array is too small to include a terminating null character */
+#pragma warning(disable:4295)
+
 #endif