speexdsp versioning

Hello,

alsa-plugins currently includes speex/speex_types.h, but that doesn't
work with speexdsp versions >= 1.2rc2, since speex_types.h has been
replaced with speexdsp_types.h. I made a patch for alsa-plugins, so that
it includes speexdsp_types.h instead. I also bumped the speexdsp version
check from "1.2" to "1.2rc2" in configure.ac, since speexdsp_types.h
didn't exist in versions prior to 1.2rc2.

The version bump will break, however, if speexdsp 1.2 will ever get
released, because I think that pkg-config considers "1.2" to be less
than "1.2rc2" (I didn't actually verify that, but considering that
pkg-config thinks that "1.2rc2" >= "1.2", it's pretty likely that "1.2"
< "1.2rc2" in pkg-config's mind).

As a solution, I propose that if a non-rc releases of speexdsp will
still be made, the 1.2 version number will be skipped, and 1.3 will be
used instead.

-- 
Tanu