Add namespace for global libmesh_abort() calls

Author: roystgnr

include/base/libmesh_exceptions.h

@@ -219,7 +219,7 @@ class TerminationException
 
 #else
 
-#define LIBMESH_THROW(e) do { libMesh::err << e.what(); libmesh_abort(); } while (0)
+#define LIBMESH_THROW(e) do { libMesh::err << e.what(); libMesh::libmesh_abort(); } while (0)
 #define libmesh_rethrow
 #define libmesh_try
 #define libmesh_catch(e) if (0)