SERVER-7080 Emulate backtrace_symbols() and backtrace_symbols_fd() on Solaris 10

backtrace_symbols() returns a block of strings, each containing a
symbolic representation of a location in a stack trace; i.e. a line
of a stack trace.  backtrace_symbols() is allowed to (and must)
allocate memory and cannot be used in a signal handler.  Add code to
produce lines on Solaris 10 that are similar to those produced by
backtrace_symbols() on Solaris 11.

backtrace_symbols_fd() writes a stack trace to a specified file
descriptor.  backtrace_symbols_fd() must not allocate memory and may
be safely used in a signal handler.  Add code to produce output on
Solaris 10 that is similar to that produced by backtrace_symbols_fd()
on Solaris 11.