Add support for call stack unwinding and function name resolution

Packages describing “unwind” as local USE flag

Package “unwind” Flag Description
dev-cpp/glog Use sys-libs/libunwind for stack unwinding instead of glibc/gcc (may be more reliable on x86_64)
dev-libs/efl Enable debug support via sys-libs/libunwind
www-apache/mod_backtrace Use sys-libs/libunwind to provide better resolution of function names.
x11-base/xorg-server Enable libunwind usage for backtraces
app-emulation/wine-staging Use sys-libs/libunwind to unwind the stack
app-emulation/wine-vanilla Use sys-libs/libunwind to unwind the stack
dev-util/perf Use sys-libs/libunwind for frame unwinding support.
dev-util/ltrace Use sys-libs/libunwind for frame unwinding support
dev-util/strace Enable stack backtraces (-k flag) via sys-libs/libunwind
dev-util/sysprof Use sys-libs/libunwind to unwind the stack
media-libs/gstreamer Enable sys-libs/libunwind usage for better backtrace support in leaks tracer module

All packages providing a “unwind” USE flag (14)