make EXTLIBS optional, depend on the library
test aio_tcp_new, stricter loop type check
aio: fix loop, add aio_last_error
aio: probe for libuv and pcre and copy it into lib/ if needed
fix static targets: libs
aio: fix more loop inits
aio: move loop to the end, make it an aio_loop object

and add mode globals: aio_run modes, aio_version, aio_version_string
aio: add run, more aio_last_error's
aio: more typechecks, more aio error handling
aio: couple of more methods. tty, pipe, stream, prepare, check, shutdown