fixup! [sieve] message.c: add :copy support to keep action
fixup! [sieve] bc_eval.c: boilerplate for hasflag test taken from header test
Revert "[sieve] update sieve_fileinto() and sieve_keep() to use :flags parameter"

This removes the actionflags parameter that we added earlier on in
implementing the imap4flags sieve extension.  Since we have removed
dependence on this parameter, we can remove it from the functions that
previously used it.
[sieve] complete removal of no-longer-used actionflags parameter

Removed actionflags parameter from do_fileinto(), do_keep(),
sieve_fileinto_context_t, and sieve_keep_context_t
[sieve] remove superfluous sieve_addflag() and _removeflag() functions

- strarray_add_case() is identical to sieve_addflag()
- strarray_remove_all_case() is identical to sieve_removeflag()
[sieve] bytecode: don't emit unused :index parameter for hasflag test

We initially used identical bytecode for header and hasflag tests.
This patch makes the bytecode formats differ by using a code position
for the :index argument only in the case of a header test.
[sieve] flags.c: fix memory leak in verify_flaglist()
fixup! [sieve] sieved: update bytecode decompiler for imap4flags