Especially when using mklog.py, it is simply to forget to fill in
the entries after the '\t* file.c (section):' or '\t(section):'.
contrib/ChangeLog:
* gcc-changelog/git_commit.py (item_parenthesis_empty_regex,
item_parenthesis_regex): Add.
(check_for_empty_description): Use them.
* gcc-changelog/test_email.py (test_emptry_entry_desc,
test_emptry_entry_desc_2): Add.
* gcc-changelog/test_patches.txt: Add two testcases for it.
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