Rewrite the query machinery in c++:
- use an MSet decorator instead of the mu-msg-iter stuff
- use mu-query-decider to mark duplicates/unreadable/related messages
- use mu-query-threader to replace the older container/thread code
Algorithm did not substantially change, but the implementation details
did.
Add some Rust-style Result/Option types, based on TartanLlama's
expected, optional classes.
There's std::optional of course, but we can't depend on C++17 yet.
- Move the lib/query/ stuff up a level into lib/
- Associate directly with the Query object
- Rework the Query object to be C++ rather than mixed with C
- Update all dependencies, tests
Using deque gives compilation errors when compiling on
MacOS/clang (where it defaults to libc++ rather than gcc's libstdc++)
```
#include <deque>
struct Foo { std::deque<Foo> foos; };
int main() { Foo foo; }
```
So, let's use a vector instead; this is a drop-in replacement here, but
unfortunately in some future code...
Seems there are problems compiling mu with XCode 11.6 (see build tests);
apparently because of libc++ being different from libstdc++.
clang++ builds works fine as long as we're using libstdc++.
If the user has wants to postpone clean-up we shouldn't lock the
indexer waiting for something that will never happen. Clear the flag
event though we are actually skipping cleanup.
When this function is declared const or pure, clang at -O1 or higher optimizes
away the call to mu_str_size_s() inside mu_str_size(), so that it ignores its
argument and returns whatever is in mu_str_size_s()'s static buffer.
Found when test-mu-str failed while testing an update of mu in OpenBSD's ports tree.
Implement a new message indexer consisting of a single-threaded scanner
and a multi-threaded indexer.
This allows for a number of optimizations as well as background
indexing, though this initial version should be behave similar to the
old indexer.
