add Exception#backtrace test
fix crash in 2nd call to vsnprintf
add verbose_backtrace
print singleton class name in verbose backtrace
support multiple filename in irep
use uint16_t for line type
reduce node size
rename debug function name
support c++ in mruby/debug.h
better line type selector
declare variable outside for
don't use RArray in filename table generating
improve checkings in debug.c
fix line number after first file
remove Exception#verbose_backtrace; #1495
MSVC: compilation works again (+minor style fixes)
BUG: mrb_irep_free (access of freed memory)
fix wrong assertion fail when debug info contains more than one files
check returning line entry pointer is greater or equal to the first line entry pointer
add comment to mrb_assert in src/debug.c