MiniScript 2.0 Preview 9

Preview build 9 of MiniScript 2.0. Changes since preview 8:

Language & semantics

• new now requires a map; __isa cycles are rejected.
• Fixed inconsistencies in how @ affects indexing.
• Fixed off-by-one error in range under certain conditions (issue #14).
• Fixed NaN == NaN comparison.
• Fixed parsing of method calls where the first argument starts with parentheses, e.g. m.f (arg1), arg2.
• Map inserts now store a frozen copy of a list or map key.
• String indexing is now by Unicode code point in both C# and C++, with surrogate pairs handled identically.
• info on a function reference now reports the source code location where it was defined.

Performance

• String indexing is now O(1) instead of O(N) in the common case.
• GC policy collects more aggressively after heavy allocation, plus new facilities for collecting at appropriate
  times automatically.
• Removed unused opcodes (this is more of a clean-up task than performance.)

Fixes

• Fixed iteration over locals in the C++ version.
• Fixed string interning in C++, and C++ string processing where a char(0) is involved.
• Fixed two register scoping issues.
• Fixed invoking an intrinsic function through a funcRef, and an intrinsic-clearing issue.
• Fixed failure to mark the intrinsics map as a GC root.
• Class short names are now cleared before the invalidation callback.

Build & embedding

• Fixed several build issues that appear on less common platforms.
• C++ function pointer typedefs changed to std::function (thanks @Mo-Tx, PR #12).
• Revised the C++ host update guide with better GC discipline guidance.