Turn on buffering for config file reads. This is dependent on ap_fgets()

doing the right thing.

Brian Havard implemented buffering for ap_fgets() on Win32 recently; OS/2 had
it already.  This provides it for Unix.

changes to ap_read(), ap_getc(), ap_fgets() for Unix:

1) this fixes a problem in where ap_open() where a lock is created for
   non-buffered files
2) this fixes problems setting rv correctly in the ap_read() buffered
   path
3) since ap_read() works as expected, it is possible to make ap_getc()
   and ap_fgets() even smaller
4) ap_fgets() no longer cares about '\r'


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@85586 13f79535-47bb-0310-9956-ffa450edef68