Fixes rust-lang#20978 for supported platforms (i.e. non-Android POSIX). This uses `backtrace_pcinfo` to inspect the DWARF debug info and list the file and line pairs for given stack frame. Such pair is not unique due to the presence of inlined functions and the updated routine correctly handles this case. The code is modelled after libbacktrace's `backtrace_full` routine. There is one known issue with this approach. Macros, when invoked, take over the current frame and shadows the file and line pair which has invoked a macro. In particular, this makes many panicking macros a bit harder to inspect. This really is a debuginfo problem, and the backtrace routine should print them correctly with a correct debuginfo.

Commits

Commits on Feb 26, 2015

std: Include line numbers in backtraces.

Removed an excess feature flag from the backtrace test.

Makes the picky tidy satisfied. Also refers to the correct issue.

Commits on Feb 27, 2015

std: Fixed backtrace warnings and tests for non-Linux platforms.