QuRT: Added HRT workqueues as per POSIX

A high rate workqueue is required that acts like an interrupt handler
for a HW timer.

Signed-off-by: Mark Charlebois <charlebm@gmail.com>

src/platforms/posix/px4_layer/px4_posix_tasks.cpp

@@ -57,7 +57,7 @@
 
 #define MAX_CMD_LEN 100
 
-#define PX4_MAX_TASKS 100
+#define PX4_MAX_TASKS 50
 #define SHELL_TASK_ID (PX4_MAX_TASKS+1)
 
 pthread_t _shell_task_id = 0;