All these stub files are generated automatically, along with .cvsignore, by a little shell script named ext_skel that resides in the ext directory.
PHP 4 features an automatic build system that's very flexible. All modules reside in a subdirectory of the ext directory. In addition to its own sources, each module consists of a config.m4 file, for extension configuration. (for example, see http://www.gnu.org/manual/m4/html_mono/m4.html)