rudimentary preparation to build pecl exts

for now we can work with a fixed source tree path, todos

- read the tarballs from the given dir
- extract and copy each one into the php-src/ext
- check some minimal stuff for the ext, like whether it's enable/with option
- check for the lib deps (can be ommited for now)
- build with php
- pack dll and pdb to some out dir (both ext and possible deps)
- push to the ftp server