Port type signal

[dalex78]

The changement are those implemented by @eschmidscs in pull request #792 with the changes requested by Lars.
Note that there is also a modification of the regex from:

code = re.sub("\bsignal\b", "", code)

to

code = re.sub(r"\bsignal\b", "", code)

otherwise the tests fail. The python documentation about the word boundary states:

There are two subtleties you should remember when using this special sequence.
First, this is the worst collision between Python’s string literals and regular expression sequences. In Python’s string literals, \b is the backspace character, ASCII value 8. If you’re not using raw strings, then Python will convert the \b to a backspace, and your RE won’t match as you expect it to.
Second, inside a character class, where there’s no use for this assertion, \b represents the backspace character, for compatibility with Python’s string literals.

[dalex78]

The 517 tests all pass (using tox -v -e py39-unit-modelsim).

[dalex78]

@LarsAsplund I suggest to merge and close this PR and to close without merging #792.

[eschmidscs]

@dalex78 Thanks for fixing the fix and properly testing it!

[umarcor]

LGTM