write_paragraph emitted a bare-space continuation line for empty lines
inside a value, which parse_paragraphs treated as a paragraph separator
and silently dropped the rest of the value; blank lines are now encoded
as ' .' like dpkg does and decoded back on read. Tab-indented
continuation lines now strip exactly one tab instead of keeping it.
Clearsigned .dsc content no longer leaks armor metadata into parsed
fields: the Hash:/Comment: header and the signature trailer are
stripped before parse_paragraphs at both .dsc parse sites.
vhaudiquet
38562abe2c