Use `_immediate_*` rules in macrocalls and quotations

[savq]

• Add _array rule for matrices, vectors and comprehensions.
• Extend closed macrocalls to work with braces and brackets.
• Refactor _quote_expression to use separate _immediate_* rules for each quotable, and to improve the parsing of syntactic operators.
• Update tests for macro calls.
• Disallow bare tuples in function_expression RHS.
• Use _ instead of $ to clarify which expressions are terminals.