RFC extensions_path directive

We have a need for a search path for extensions, so that we can have a system provided set of extensions and an optional location for per-application extensions that either augment or override the baseline extensions. To facilitate this, I propose that we create a new directive called extensions_path that allows the sysadmin to configure a search path for extensions. I see the usage as going something like this: extensions_path = "/local/extensions:$DEFAULT_EXTENSIONS_DIR" Where $DEFAULT_EXTENSIONS_DIR evaluates to the default value of extensions_dir. I think it's important to have a symbol for the default location, so that httpd.conf files don't have to have our API numbers encoded into them. I don't mind if the actual symbol we use for the default manifests differently, so long as it works from within httpd.conf... if extensions_dir works there. If it's php.ini only, I'm happy to use the existing constant expansion stuff we have for php.in... if that will work in a path string syntax. I also don't mind if we simply expand extensions_dir to behave in this manner. I just want to gather some feedback before writing some code. To be super clear, I don't propose changing anything other than the searching behavior for extensions. --Wez.