Patch from Bill. r+ from me.
This removes SeaMonkey's reliance on being a subconfigure. This was necessary after the completion of Bug 1490765.
The moztopsrcdir, commtopsrcdir and related variables are retained.
Per Fallen this saves a lot of editing, and makes the patch far less intrusive.
- Move remaining suite/configure.in pieces to moz.configure
- Move moz* and comm* variables from confvars.sh to moz.configure
- Remove configure.in
MOZ_RUST_URLPARSE can go because it was removed in Bug 1415206.