escape names interpolated into source-matching patterns

[alhudz]

Repro: set Baz.__name__ = r'\w+' on any class and call dill.source.getsource(Baz). It returns the source of a different class defined later in the same file. With Baz.__name__ = 'Baz((' it raises re.error rather than the IOError the function documents.

Cause: findsource concatenates __name__ straight into the class-definition pattern, so a name that is not an identifier is matched as a pattern instead of literally. __name__ is freely assignable and is not required to be an identifier. _closuredimport builds its two candidate patterns from getname() the same way, and getname() can return a repr containing brackets even for ordinary objects.

Fix: re.escape the interpolated names at the three sites. re.escape leaves identifiers untouched, so behaviour for ordinary names is unchanged. Test added covers both the wrong-match and the uncompilable name.