php_crypt.dll missing in php4 win32 binary dist?

php.ini contains an extension pointer to php_crypt.dll but no such file is included with php4 (there was a php3_crypt.dll with php3). Therefore (I assume) crypt() fails. I wasn't able to find an answer this in the lists, other than to note others had similiar issues. Anyone know what this is all about? Also, many other extension dll files that came with php3 are missing in php4. Why? Are the php3 versions of these dlls compatible with php4? Lastly, I read that mysql support is compiled into php4. Oddly tho, that's one of the few extension dlls that still come with php4. Did I misunderstand? Thanks