Move abrt-backtrace app from src/Backtrace/main.c to src/utils/abrt-backtrace.
Move backtrace preprocessign code from abrt-backtrace to the parser.
Implemented new backtrace rating algorithm.
Added old bt rating algorithm to backtrace.c
Move strbuf to lib/Utils, and updated it to use xfuncs.
Created separate header for xfuncs.
Some functions in xfuncs marked as extern "c", so they can be used
in C code.
Merged backtrace fallback (independent_backtrace) "parser" into
backtrace.{h/c}.
Added option --rate to abrt-backtrace, to be able to use the new
backtrace rating algorithm in scripts.