v1.6 - RISC-V, Apple Sillicon, libunwind, C++17

Notable additions:

• RISC-V mcontext.
• Support for Apple Silicon.
• libunwind for Linux and macOS.
• C++17 compatibility.

The rest is all bug fixes.

Summary of changes in no particular order.

Alexey Ochapov (1):

• 23b9050 specify that variable values in stacktraces are not supported currently

Andreas Schwab (1):

• f5f329f Add support for RISC-V mcontext

Anonymous Maarten (4):

• 7272606 Use lowercased Windows SDK headers
• ee814f1 Only define NOMINMAX if not defined already
• 8bf0e1c Only do '#pragma comment(lib, "xxx.lib")' on MSVC
• 146e2ed cmake: link to dbghelp, psapi and msvcr90 on mingw

Brad Tighe (1):

• 032207f fix #208. TraceResolverImpl<system_tag::windows_tag> does not inherit from a base class, but as of #162 the resolve method is marked override, causing a compiler error.

Christophe Bedard (3):

• 2c9d878 Fix unushed parameter warnings
• 9e20b2e Add empty virtual destructor to TraceResolverImplBase base class
• bfa0c9b Fix NAME_MISMATCHED arg error on CMake>=3.17

Emre Ataseven (1):

• 9f49ea3 fix typo in variable name

François-Xavier Bourlet (30):

• 29e4061 clang-format
• e82d107 Remove outdated build status badge
• f6f7253 Typo #elif -> #else

Ilya A. Kriveshko (1):

• 84b1111 fix memory leak from demangle

Martin Gerhardy (2):

• 738e3c6 Fix invalid memset call
• d1ce8ba Fixed a few compile errors

Michael Truog (1):

• 74dd7d6 Fix for C++ compilers without C++11

Oliver Old (3):

• c9f2b47 Don't pass buffer as format string and free buffer
• 067fb09 Fix wrong condition
• d34e460 Fix indentation

Pedro Navarro (3):

• ca5480c Fix rare crash when looking for a function name
• 6084a39 DW_AT_call_file is an unsigned value
• a8a2efd Added libunwind support to Linux and macOS

Philip Rader (1):

• 72970bf Add support for Apple Silicon

Przemyslaw Olejniczak (1):

• 4f1a691 MSVC: does not compile with Unicode/Multi-Byte character set

Tomislav Zubcic (1):

• f7ad514 Fix compilation issue on windows.

Vladislav Shpilevoy (3):

• 220eda3 Introduce TraceResolver::load_addresses() for raw address array
• a9b2ab5 Make bfd_fileobject accessed by pointer
• f093895 Use /proc/self/exe as the last resort for libbfd

c99 (2):

• 42df989 Add for std::back_inserter
• 5d1d610 Fix printing stack trace under Windows.

hshakula (1):

• 0b4483f Fix compilation error with C++17 compiler

rulerOfTheHuns (1):

• 04efb6f fix output on windows #204

tomdov (1):

• 10c8df5 size() may return negative number

xgdgsc (2):

• 643bccc add note for folly users
• 0905992 fix #188. Cmake warning on find_package(Backward).