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/cmake/FindVorbisEnc.cmake

@@ -0,0 +1,64 @@
+# - Find vorbisenc
+# Find the native vorbisenc includes and libraries
+#
+#  VORBISENC_INCLUDE_DIRS - where to find vorbisenc.h, etc.
+#  VORBISENC_LIBRARIES    - List of libraries when using vorbisenc.
+#  VORBISENC_FOUND        - True if vorbisenc found.
+
+if (VORBISENC_INCLUDE_DIR)
+	# Already in cache, be silent
+	set (VORBISENC_FIND_QUIETLY TRUE)
+endif ()
+
+find_package (Vorbis QUIET)
+
+find_package (PkgConfig QUIET)
+pkg_check_modules (PC_VORBISENC QUIET vorbisenc)
+
+set (VORBISENC_VERSION ${PC_VORBISENC_VERSION})
+
+find_path (VORBISENC_INCLUDE_DIR vorbis/vorbisenc.h
+	HINTS
+		${PC_VORBISENC_INCLUDEDIR}
+		${PC_VORBISENC_INCLUDE_DIRS}
+		${VORBISENC_ROOT}
+	)
+
+find_library (VORBISENC_LIBRARY
+	NAMES
+		vorbisenc
+		vorbisenc_static
+		libvorbisenc
+		libvorbisenc_static
+	HINTS
+		${PC_VORBISENC_LIBDIR}
+		${PC_VORBISENC_LIBRARY_DIRS}
+		${VORBISENC_ROOT}
+	)
+
+# Handle the QUIETLY and REQUIRED arguments and set VORBISENC_FOUND
+# to TRUE if all listed variables are TRUE.
+include (FindPackageHandleStandardArgs)
+find_package_handle_standard_args (VorbisEnc
+	REQUIRED_VARS
+		VORBISENC_LIBRARY
+		VORBISENC_INCLUDE_DIR
+		VORBIS_FOUND
+	VERSION_VAR
+        VORBISENC_VERSION
+	)
+
+if (VORBISENC_FOUND)
+	set (VORBISENC_INCLUDE_DIRS ${VORBISENC_INCLUDE_DIR})
+	set (VORBISENC_LIBRARIES ${VORBISENC_LIBRARY} ${VORBIS_LIBRARIES})
+    if (NOT TARGET Vorbis::VorbisEnc)
+		add_library (Vorbis::VorbisEnc UNKNOWN IMPORTED)
+		set_target_properties (Vorbis::VorbisEnc PROPERTIES
+			INTERFACE_INCLUDE_DIRECTORIES "${VORBISENC_INCLUDE_DIR}"
+			IMPORTED_LOCATION "${VORBISENC_LIBRARY}"
+			INTERFACE_LINK_LIBRARIES Vorbis::Vorbis
+		)
+	endif ()
+endif ()
+
+mark_as_advanced (VORBISENC_INCLUDE_DIR VORBISENC_LIBRARY)