No mutex initialisation for data_sample_lock in lp_main.cpp

[dmcnaugh]

In the frontpanel module lp_main.cpp there are 2 mutexes defined:

//static pthread_mutex_t data_lock;
pthread_mutex_t data_lock;
pthread_mutex_t data_sample_lock;

however, only the first one is ever initialised in start_threads()

pthread_mutex_init(&data_lock,NULL);

So every call to lock and unlock this mutex fails, although this does not appear to effect the operation of the frontpanel library. So there are 2 alternatives:

1. initialise the second mutex in start_threads()

   pthread_mutex_init(&data_lock,NULL);
   pthread_mutex_init(&data_sample_lock,NULL);

   or

2. remove the references in lp_main.cpp and lpanel.cpp to:

   pthread_mutex_lock(&data_sample_lock);
   ...
   pthread_mutex_unlock(&data_sample_lock);

There is a proposed fix in Pull-Request #6

[udo-munk]

Certainly an old bug missed so far. Fixed, thanks.