Users have reported errors with Apache. Enable DSO to try to fix.

Most of these vars default to no since we're cross-compiling. Change them
to on since all the libc's that OpenWrt supports supports these. epoll for
example should have better stability.

Changed PKG_LICENSE to SPDX.

Slight cleanups.

Signed-off-by: Rosen Penev <rosenp@gmail.com>