fix: rework translation-unit top-level items to disallow binary expressions & rework top level function definition pointer association

Previously, pointers were associated with the function identifier, now they're associated with the return type

This resolves conflicts with declarations that can be interpreted as binary_expressions

feat: C23

feat: allow type_qualifiers after typedef specifier, alias char content

feat: add else_clause

fix: add compound statement to call expression

* feat: allow identifiers in string concatenations

Resolves errors in strings of the form:

   ("failed in line %" PRIdLINENR)

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Co-authored-by: Lewis Russell <lewis6991@gmail.com>

fix: allow preproc define without value to preceed a line with whitespace

add multi-bitfield structs and enums with underlying types

Adding support for offsetof

Fix AppVeyor CI builds

Update used Windows image and NodeJS version to the latest LTS

Add _Noreturn, __restrict__, and _Generic

_Generic is a C11 feature, __restrict__ and _Noreturn were added to type_qualifiers

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fix: comments can have multiple delimiting backslashes

Support optional consequences

It's allowed in gcc and clang

fix: implement Unicode identifiers

According to cppreference, identifiers are `(XID_Start | '_')
XID_Continue*`, which is the case as of C++23 and C2x. I have confirmed
this myself with the drafts of C++23 and C2x.

https://en.cppreference.com/w/cpp/language/identifiers

Clang indeed implements identifiers as `(XID_Start | '_') XID_Continue*`
in C++ mode and C2x mode, with a slight extension to the character set
to include some extra math characters:
231992d9b8/clang/lib/Lex/Lexer.cpp (L1517-L1530)

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