Fix handling of multi-line function declarations

[kajakaj]

Resolves #684

The cause of this problem is the method of checking whether a particular clause should be excluded. In a file parser.py in function _raw_parse (line 161) only the line that ends with : is checked for excluded expressions, not all the lines in a statement that ends with a colon. The solution is to add checking if at least one line in the multi-line statement ended with : has to be excluded and if that is the case - to exclude that clause. Multi-line statements are added after a token \n, so after checking for excluded clauses in one-line statements. Because of that, checking if a clause after multi-line statement should be excluded was added starting from the line 193.
Tests with different use cases were added.

[nedbat]

Thanks, this looks promising. I will take a look soon.

[nedbat]

I'm going to merge this. I've thanked Jan Rusak in the changelog and contributors file. I'll gladly add other names, but I'm not sure what they are! :)

[kajakaj]

Thanks - we did it together: Jan Rusak, Maciej Kowalczyk and Joanna Ejzel.

[nedbat]

Thanks again, I added the names in 470e086

[nedbat]

This is now released as part of coverage 7.3.3.