This commit adds support for generating backtraces on Windows and
refactors the isc_backtrace API to match the Linux/BSD API (without
the isc_ prefix)
* isc_backtrace_gettrace() was renamed to isc_backtrace(), the third
argument was removed and the return type was changed to int
* isc_backtrace_symbols() was added
* isc_backtrace_symbols_fd() was added and used as appropriate
The previous commit removed the code related to the internal symbol
table. On platforms where available, we can now use backtrace_symbols()
to print more verbose symbols table to the output.
As there's now general availability of backtrace() and
backtrace_symbols() functions (see below), the commit also removes the
usage of glibc internals and the custom stack tracing.
* backtrace(), backtrace_symbols(), and backtrace_symbols_fd() are
provided in glibc since version 2.1.
* backtrace(), backtrace_symbols(), and backtrace_symbols_fd() first
appeared in Mac OS X 10.5.
* The backtrace() library of functions first appeared in NetBSD 7.0 and
FreeBSD 10.0.
