1. Moved the declaration of the osrf_host_config struct out of the header.

1. Moved the declaration of the osrf_host_config struct out of the header.
Nothing outside of osrf_settings.c needs access to any members of this
struct.

2. Made the osrf_settings_new_host_config function static; removed its
prototype from the header.

3. Made the "config" pointer static.

4. Rearranged osrf_settings_free_host_config a bit to protect against
attempts to free the cached config twice.

5. Finished adding doxygen-style markup comments.

git-svn-id: svn://svn.open-ils.org/OpenSRF/trunk@1771 9efc2488-bf62-4759-914b-345cdb29e865