Issue 32222: pygettext doesn't extract docstrings for functions with type annotated params

### Expected Behaviour
When running pygettext with the -D CLI flag, all module, class, method and function docstrings should be extracted and outputted to the .pot file.

### Actual Behaviour
In the case of functions whose parameters have PEP 484 type annotations, their docstrings are not being extracted. I have attached two files, one .py file and its corresponding .pot file, as examples of this behaviour.

Correction for above: the type annotation syntax is actually from PEP 3107, not PEP 484.

I should also point out that this behaviour is occurring for annotated return types of functions and methods as well.

This is occurring on both Windows and Linux.

Another correction; I said that this is occurring for return type annotations; this is not true. This is only occurring for functions with annotated *arguments*.

The cause of this issue is in pygettext's TokenEater.__suiteseen method. This method eats tokens until it sees a colon operator, after which it assumes a function docstring may follow. In the case of a function with annotated arguments, obviously this is incorrect, as colons would appear before the final colon of the 'suite'.

New changeset eee72d4778a5513038edd5236cdd87ccce2bc60a by Serhiy Storchaka (Tobotimus) in branch 'master':
bpo-32222: Fix pygettext skipping docstrings for funcs with arg typehints (GH-4745)
https://github.com/python/cpython/commit/eee72d4778a5513038edd5236cdd87ccce2bc60a

New changeset 51d95ffc2fb3337dc87277c9af25ecc9a01f991b by Miss Islington (bot) in branch '3.7':
bpo-32222: Fix pygettext skipping docstrings for funcs with arg typehints (GH-4745)
https://github.com/python/cpython/commit/51d95ffc2fb3337dc87277c9af25ecc9a01f991b

I think this is resolved and can be closed.

nosy: + serhiy.storchaka
versions: + Python 3.7, - Python 3.5

messages: + msg307654