saves a few lines in the dumper implementations for the 'putEllipses' logic.

This is an attempt to make it work with released gdb 7.0. It uses some
ugly workarounds to compensate for the missing gdb.Block and gdb.Symbol
structures.

It is nicer in the presence of namespaces as '::' will be replaced by '__'
to create the dumper function names.

Introduce Dumper.put{Value,Name,StringValue,ByteArrayValue} functions.
No need for explicit specification of valueencoding in user code.

more robustness in case qt's namespace cannot be determined
work on qvariant dumper