c++: array concatenation, string indexing, better lexer errors, prelude

[Spongman]

• array concatenation
• string indexing
• better lexer errors
• prelude (TsRustZigDeez -f prelude)
• make install
• make docker-repl
• update gtest version
• fix gcc12 warnings
• reduce string allocations in environment get/set
• add fibonacci test (borrowed from lisp versions)
• move builtins & infix operators to global environment
• optimize infix eval
• add '$' unary operator, simplify some prelude functions
• rename cpp->cpp-spongman

[vhladko]

@nicdgonzalez may I ask you review it ? :)

[vhladko]

@Spongman okay, so just to clarify, this MR not only creates an additional copy of cpp folder, but also "revert" cpp folder to initial commit by @nicdgonzalez , right ?

[Spongman]

no, i'm not sure how to do that.;

[vhladko]

I'm just confused a little bit, that diff shows removing from cpp, Dockerfile, Readme etc

[vhladko]

okay, so let me merge this one, and then I'll try to restore the original cpp folder with initial commit.

[Spongman]

great, thanks!