Issue #9979: Use PyUnicode_AsWideCharString() in import.c
Issue #9979: Use PyUnicode_AsWideCharString() in import.c

Don't truncate path if it is too long anymore, and allocate fewer memory (but
allocate it on the heap, not on the stack).

sk-/python2.7-type-annotator,sk-/python2.7-type-annotator,sk-/python2.7-type-annotator