lua Add scrollable stack traceback WIP

lua currently splashes a stack traceback on error
for deep tracebacks and especially on devices with smaller screens
this leaves out a lot of vital information

in the past I have resorted to splitting the traceback string or
even saving the return to a file

This patch provides a scrollable buffer with rudimentary text reflow
to allow you to read the whole traceback string

Upon traceback if you press nothing the screen will display for 5 seconds
If you press OK or CANCEL it will quit immediately
PREV/NEXT scrolls the list on button press timeout is disabled

lua now provides rb.splash_scroller(timeout, str)

example script provided too

Change-Id: Idbc8ce0c514196f0fae48c43aeaea8b60d6da1a5

apps/plugins/lua/rockconf.h

@@ -48,6 +48,7 @@ unsigned long strtoul(const char *str, char **endptr, int base);
 size_t strftime(char* dst, size_t max, const char* format, const struct tm* tm);
 long lfloor(long x);
 long lpow(long x, long y);
+int splash_scroller(int timeout, const char* str);
 
 #define floor   lfloor
 #define pow     lpow