Add missing build dependency to libosmocodec-dev

Since I0190872dd282bcfe0f97bb4f8ab8d09023f9f06b we are using a header
file provided by libosmocodec, which means we need to add it to our
dependencies (and include path).  Linking against the library is
not required, as we don't use any symbols at this point.

Change-Id: Ie4524165d8873f6c801e07d9f03c94f43c66110d
diff --git a/configure.ac b/configure.ac
index 04ffca6..d24010e 100644
--- a/configure.ac
+++ b/configure.ac
@@ -67,6 +67,7 @@
 PKG_CHECK_MODULES(LIBOSMOCORE, libosmocore >= 1.1.0)
 PKG_CHECK_MODULES(LIBOSMOVTY, libosmovty >= 1.1.0)
 PKG_CHECK_MODULES(LIBOSMOGSM, libosmogsm >= 1.1.0)
+PKG_CHECK_MODULES(LIBOSMOCODEC, libosmocodec >= 1.1.0)
 PKG_CHECK_MODULES(ORTP, ortp >= 0.22.0)
 
 AC_ARG_ENABLE([dahdi],