Version 6.1

The following C++20 features are now supported:

- Concepts (see Changes entry and C++20 feature table for more information)
- Defaulted comparison specification cleanups
- Allow pack-expansions in lambda init-captures
- Efficient sized delete for variable sized classes
- Checking for abstract class types
- Permitting trivial default initialization in constexpr contexts
- Conditionally trivial special member functions
- Adding the constinit keyword
- Allow defaulting comparisons by value
- Remove std::strong_equality and std::weak_equality
- Coroutines clarifications (see Changes entry and C++20 feature table
  for more information)
- Enabling constexpr intrinsics by permitting unevaluated inline-assembly
  in constexpr functions
- Converting from T* to bool should be considered narrowing
- Make "typename" more optional

Our current C++20 implementation status (and links to the associated
standards committee papers) is available here:

    https://www.edg.com/cpp20_features.html

We now also support a C++17 feature for which we previously only had partial
support: Rewording inheriting constructors (P0136R1).

We are in the process of implementing modules.  We don't make any claims
about support for modules in this release.

Our initial support of modules (date not yet known) will support the
consumption of Microsoft module files.  Module support is disabled by
default but you can enable that with the --modules option.  Consuming
Microsoft module files means importing IFC files produced by the Microsoft
compiler.  The compatibility of those files has strong dependence
on the particular version of the Microsoft compiler used to produce the files.
This beta can consume files produced by a pre-release version of the Microsoft
compiler (19.27.28827.95), so it is unlikely that you will be able to use
that feature.

The front end contains these new source files:
  ifc_modules.c
  ifc_modules.h
  modules.c
  modules.h

This is our second release that must be built as C++ code.  The minimum
compiler requirements have not changed, so they continue to be:

     g++: 4.7.0 (it does not work with 4.6)
     clang: 3.2 (the oldest version we have tried)
     MSVC: VS 2015 (tested with build 19.00.24215.1)

The front end can be self-compiled with a C-generating back end version for
platforms that lack a native C++ compiler.   We do not use exception
handling or RTTI, so those can be disabled when self-compiling to produce
more efficient code.

We do not use the standard library specified in the C++ standard.  So if your
code uses the standard library you don't have to worry about our possible use
of an incompatible version of the library.

The builtin function support incorporates changes in the GCC builtin function
signatures through GCC version 10.2.0 and in the clang builtin function
signatures as of clang 10.0.0.

As usual, we have fixed bugs, added many minor features, and continued to
improve our various compatibility modes.  See the Changes_6.1 file for
full details (about 5,400 lines).
