BigBuf and tracing rework: allow much longer traces in in hf commands

- provided a BigBuf_malloc() function to dynamically allocate parts of BigBuf
  e.g. for DMA-Buffers, Frame-Buffers, Emulator-Memory
- the whole rest of BigBuf is now available for traces (instead of a small fixed amount)
- send actual traceLen together with trace data
- changed client side to cope with varying traceLen
- changed small buffers to automatic variables instead of parts of BigBuf

client/data.h

@@ -13,13 +13,9 @@
 
 #include <stdint.h>
 
-//trace buffer size as defined in armsrc/apps.h TRACE_SIZE
-#define TRACE_BUFFER_SIZE 4096
 #define FILE_PATH_SIZE 1000
-#define SAMPLE_BUFFER_SIZE 64
 
 extern uint8_t* sample_buf;
-extern size_t sample_buf_len;
 #define arraylen(x) (sizeof(x)/sizeof((x)[0]))
 
 void GetFromBigBuf(uint8_t *dest, int bytes, int start_index);