#44 Cinelerra 7 fix for compiler warning file g72x_priv.h

[Mat Nieuwenhoven]

System Mint 18.3 (base: Ubuntu 16.04), 64 bit, AMD cpu, compiler 5.4.0 . The compiler gives a warning on the file about an implicit function declaration. This patch fixes it. Apply as "patch -p1 <g72x_priv.h.patch" in the thirdparty/libsndfile-1.0.11/src/G72x/ directory.
On Mint 17.3 (Ubuntu 14.04) the compiler doesn't detect this.