Update libsndfile to 1.0.29pre2+git

This pulls in MANY (over 890) changes compared to our
from our current 1.0.24 version.

lib-src/libsndfile/Scripts/linux-to-win-cross-configure.sh

@@ -0,0 +1,22 @@
+#!/bin/bash
+
+case "$1" in
+	w32)
+		compiler_name=i686-w64-mingw32
+		;;
+	w64)
+		compiler_name=x86_64-w64-mingw32
+		;;
+	*)
+		echo "$0 (w32|w64) <other args>"
+		exit 0
+		;;
+	esac
+
+shift
+
+build_cpu=$(dpkg-architecture -qDEB_BUILD_GNU_CPU)
+build_host=$build_cpu-linux
+
+./configure --host=$compiler_name --target=$compiler_name --build=$build_host \
+		--program-prefix='' --disable-sqlite --disable-static $@