unwind: demangle symbol names

unwind: demangle symbol names

Implement demangling of C++ symbol names in stack trace
using cplus_demangle function from GNU libiberty library.

This is an example demangled stack trace output:

fstat(5, {st_mode=S_IFREG|0664, st_size=0, ...}) = 0
 > /usr/lib64/libc-2.25.so(__fxstat64+0x12) [0xffd62]
 > /usr/lib64/libc-2.25.so(_IO_file_doallocate+0x5f) [0x717ff]
 > /usr/lib64/libc-2.25.so(_IO_doallocbuf+0x79) [0x81699]
 > /usr/lib64/libc-2.25.so(_IO_file_overflow+0x198) [0x807b8]
 > /usr/lib64/libc-2.25.so(_IO_file_xsputn+0xbd) [0x7ed5d]
 > /usr/lib64/libc-2.25.so(fwrite_unlocked+0x60) [0x7d800]
 > /usr/lib64/libleveldb.so.1.18(leveldb::EnvWrapper::StartThread+0x3b6) [0x48656]
 > /usr/lib64/libleveldb.so.1.18(leveldb::log::Writer::EmitPhysicalRecord+0x89) [0x28bc9]
 > /usr/lib64/libleveldb.so.1.18(leveldb::log::Writer::AddRecord+0x9e) [0x28d9e]
 > /usr/lib64/libleveldb.so.1.18(leveldb::DBImpl::Write+0x208) [0x1ce18]
 > /usr/lib64/libleveldb.so.1.18(leveldb::DB::Put+0x59) [0x192b9]
 > /usr/lib64/libleveldb.so.1.18(leveldb::DBImpl::Put+0x1d) [0x1931d]
 > /home/yamato/var/leveldb/doc/a.out(main+0x120) [0x1107]
 > /usr/lib64/libc-2.25.so(__libc_start_main+0xea) [0x2088a]
 > /home/yamato/var/leveldb/doc/a.out(_start+0x2a) [0xf3a]

* Makefile.am [USE_DEMANGLE] (strace_CPPFLAGS, strace_LDFLAGS,
libiberty_LDADD): Append libiberty_CPPFLAGS, strace_LDFLAGS, and
libiberty_LIBS, respectively.
* configure.ac: Add --with-libiberty option.  Check cplus_demangle
support in libiberty.
* unwind.c [USE_DEMANGLE]: Include <demangle.h>.
(print_stack_frame) [USE_DEMANGLE]: Use cplus_demangle.

Signed-off-by: Masatake YAMATO <yamato@redhat.com>