loadlibrary.c: Exclude line from coverage

.. as it seems that something in Windows/Wine would need to be off
to execute it.
diff --git a/expat/lib/loadlibrary.c b/expat/lib/loadlibrary.c
index 452ae92..35fdf98 100644
--- a/expat/lib/loadlibrary.c
+++ b/expat/lib/loadlibrary.c
@@ -84,7 +84,7 @@
   /* Get a handle to kernel32 so we can access it's functions at runtime */
   HMODULE hKernel32 = GetModuleHandle(TEXT("kernel32"));
   if(!hKernel32)
-    return NULL;
+    return NULL;  /* LCOV_EXCL_LINE */
 
   /* Attempt to find LoadLibraryEx() which is only available on Windows 2000
      and above */