Replace of ... end with braces

[AshleyYakeley]

Remove of, end, in keywords, add ap keyword.

• ap { ... }
• do { ... }
• match { ... }, see Replace match with fn of (or fn {}) #313
• namespace N { ... }
• datatype N { ... }
• Mk { ... }
• rf { ... } -- a record function, not a keyword
• let { ... } expr
• let rec { ... } expr
• imply { ... } expr
• with { ... } expr
• import { ... } expr

Option

• with ... expr (one namespace only, or allow comma-separated)
• import ... expr (one file only, or allow comma-separated)

Option

Declarators

• let { ... }
• let rec { ... }
• with x, y
• import "a", "b"

Declarations

• <declarator>;
• <declarator> in <declaration>

Expression

• <declarator> in <expression>

[AshleyYakeley]

Runs into a semi-ambiguity:

• datatype T {-p,+q}
• datatype T {Mk}