package/speexdsp: new package

package/speexdsp: new package

Quoting speex release notes from https://www.speex.org

"Speex 1.2rc2 and SpeexDSP 1.2rc2 are out
 December 6, 2014
 This release splits the speex codec library and the speex DSP library
 into separate source trees."

After bumping speex to 1.2.0 this new package is necessary to provide
speex-based DSP support for packages like Freeswitch and Asterisk.

We use current git HEAD which received 21 commits since the 1.2rc3
tarball was released in 2015, including a fix for building on arm.

We still need another patch which was not committed to git master to
fix building on aarch64.

Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>