Fix for cygwin symbol visibility - sometimes _WIN32 may be defined even on cygwin.

Fixes #4670.

[SVN r65530]

libs/config

@@ -1 +1 @@
-Subproject commit dca79a5e179cdc8a5c9867790ff0f25204fd6e37
+Subproject commit c02ec6995d15e70ed83136a227b47e8b3c0d4b58