Fix topology name and namespace when one of them is an SPL reserved word

[ghost]

resolves #2474
The resolution is, that tokens in the namespace, which are SPL keywords, are replaced by __spl_ + some hash. Name and namespace are manipulated anyway, for example, non-word characters are removed, and empty tokens should be dropped. "Should be", because it did not work.

def _fix_namespace(ns):
    ns = str(ns)
    sns = ns.split('.')
    if len(sns) == 1:
        return re.sub(r'\W+', '', ns, flags=re.UNICODE)
    for i in range(0,len(sns)):
        sns[i] = re.sub(r'\W+', '', sns[i], flags=re.UNICODE)

    for i in range(len(sns), 0):     ## <<< range(len(x), 0) does NO iteration. If it did, next line raised IndexOutOfBounds
        if len(sns[i]) == 0:
            sns.pop(i)

    return '.'.join(sns)

The Java code generation has a test for vaild identifiers regular expression, but does not test for reserved words. As the function is used at many places, I decided, to not touch it.