#27 identifiers list by function/method

[Marcos Dione]

one report pychecker could do is to list the identifiers that
appear on each method or function, may be sorted alfabetically,
so it's easier to detect typos, specially on assigments. e.g.:

def main (*unused):
factor1= 73
factor2= 736

resutl= factor1*factor2

print result

the report should look like:

main:
factor1
factor2
result
resutl
unused

it's easier to find out that resutl is the typo and not result, as it
is reported now by pychecker:

pycheck.py:7: No global (result) found