ext/soundtouch/: Make pitch element controllable via GstController interface (#344821).

ext/soundtouch/: Make pitch element controllable via GstController interface (#344821).

Original commit message from CVS:
Patch by: Wouter Paesen  <wouter at kangaroot net>
* ext/soundtouch/Makefile.am:
* ext/soundtouch/gstpitch.cc:
Make pitch element controllable via GstController interface
(#344821).
* configure.ac:
Up core requirements to 0.10.8.1/CVS because earlier
GstControllers can't handle float properties correctly.
Check for GstController CFLAGS and LIBS.
* tests/icles/Makefile.am:
* tests/icles/pitch-test.c: (main):
Add small test program for the above (welcome to the 80s!).