An updated ESP8266 panic function can print out the calling function/line
and size requested for the last malloc/realloc/calloc/new allocation that
failed, without the overhead of full the OOM stack.

Add parsing for this line, when present, and output the function, file,
line, and amount of memory requested to the display.  When not present,
do nothing different.

Addr2line on the xtensa seems to have trouble with identifying the
proper file:line number for an exception address.  Until there is a
fix, the workaround is to use GDB to locate them.

See jcmvbkbc/binutils-gdb-xtensa#5 .

Replace the addr2line processing/formatting with gdb's formatting,
leaving the output identical with one exception:  addresses with
no source code (i.e. not code, but constant data somewhere or just
random variables on the stack) *will not print*.  They're silently
ignored in the output.

This also now presents the EPC1/PC and EXCVADDR on their own
lines hilighted at the top of the dump.

Additionally, handle the case where the exception dumper itself
on the ESP8266 hits the WDT (i.e. during dump of an infinite
recursion).  In this case the final "<<<stack<<<" line may not be
generated, so simply parse everything from ">>>stack>>>" to the end.