roken: win32 dlopen use LoadLibraryEx AltSearchPaths

LoadLibrary() is unable to load DLLs which are being loaded from
a global side by side assembly directory.   Instead, use

  LoadLibraryEx() with LOAD_WITH_ALTERED_SEARCH_PATH

This permits a DLL to be loaded from the WinSxs tree when a fully
qualified path is provided.

Change-Id: I0e5da1a8610c6b571f73c0e7b0beabeecbbb3b77

lib/roken/dlfcn_w32.c

@@ -144,7 +144,7 @@ dlopen(const char *fn, int flags)
 
     old_error_mode = SetErrorMode(SEM_FAILCRITICALERRORS);
 
-    hm = LoadLibrary(fn);
+    hm = LoadLibraryEx(fn, 0, LOAD_WITH_ALTERED_SEARCH_PATH);
 
     if (hm == NULL) {
 	set_error_from_last();