Fix strndup of NULL, add auto length for SCPI_ErrorPushEx

Jan Breuer

2016-04-24 1f77a03fa02b0cdbaa878cd7015838638eedc4a8

 libscpi/inc/scpi/config.h

@@ -277,7 +277,7 @@
#endif
#else
#define SCPIDEFINE_DESCRIPTION_MAX_PARTS                1
#define SCPIDEFINE_strdup(h, s, l)                      NULL
#define SCPIDEFINE_strndup(h, s, l)                     NULL
#define SCPIDEFINE_free(h, s, r)
#endif