Fix creation of the config directory used by DarwinStreamingServer.

There is no REQUIRE_DIRS used by pkgsrc.  I think that REQD_DIRS
was meant to be used; however, REQD_DIRS is also the wrong way to
create the config directory.

Set PKG_SYSCONFSUBDIR to "streaming" to automatically create
${PKG_SYSCONFBASE}/streaming during package installation, and
consistently use ${PKG_SYSCONFDIR} within the package Makefile to
refer to the config directory path.

Bump the PKGREVISION due to the changes in the resulting package
scripts.

(jlam)