i18n: use actual filename, in which function is defined, for hg.pot Before this patch, source filename for msgid in hg.pot file becomes incorrect, if a function is defined in file A, but detected in dict in file B, For example, almost all debug* commands are defined in debugcommands.py, but hggettext detects them in "table" of commands.py. Therefore, docstring fragments of debug* commands are marked as "defined in commands.py" in hg.pot file. This is serious problem for translation, because the cost to find out original location of texts increases very much.