The str_append_n() function is now deprecated. At no occasion, the occurence of
NUL in the data is possible or relevant, so each instance is replaced with
str_append_data() rather than str_append_max().

Found with clang -Wstrict-bool.

Fixed bug in the order of default argument processing. Variable strings were evaluated befor constant strings, which is wrong.

Encoded-character: resolved error reporting issue, added some syntax error tests and fixed some parsing bugs in the process.

Added the concept of persistent tags and implemented imapflags extension for bare keep and fileinto commands (intermittent commit, not working properly yet).

Properly implemented dumping a binary including a list of required extensions and support for extension-specific output.