[cpp] Fixes to sox compatibility

bob/io/audio/cpp/writer.cpp

@@ -69,7 +69,11 @@ bob::io::audio::Writer::Writer(const char* filename, double rate,
   siginfo.rate = rate;
   siginfo.precision = bits_per_sample;
   siginfo.channels = SOX_UNSPEC;
+#ifdef SOX_UNKNOWN_LEN
   siginfo.length = SOX_UNKNOWN_LEN;
+#else
+  siginfo.length = -1;
+#endif
 
   const char* extension = lsx_find_file_extension(filename);
 

bob/io/audio/version.cpp

@@ -6,12 +6,13 @@
  */
 
 #define BOB_IMPORT_VERSION
-#include <cstring>
 #include <bob.blitz/config.h>
 #include <bob.blitz/cleanup.h>
 #include <bob.core/config.h>
 #include <bob.io.base/config.h>
 
+#include <cstring>
+
 extern "C" {
 #include <sox.h>
 }