Add a top-level Cargo.toml.
Remove the vestigial libclamav_rust/Makefile.am.
Place Rust source under a libclamav_rust/src directory as is canonical
for Rust projects.
Convert cli_dbgmsg to inline function to ensure ctx check for debug flag
is always run
Add copyright and licensing info
Fix valgrind uninitialized buffer issue in cliunzip.c
Windows build fix