Change in core[master]: restore --enable-symbols option again -- was FYI: Cleanup of debug options

[Tor Lillqvist]

Argh, I hate myself for continuing this thread, but.... isn't there a
risk that people will think "--enable-backtrace" is related to the
code we have (but have disabled for some reason?), or used to have, to
display backtraces in the application itself, when it notices some
fatal signal/exception (but still is alive enough to be able to
display a backtrace)?

--tml