Preserve generated strings until consumed by formatting.
bugfix from premature push
Address review comments
Last fix(?)
Use %s formatting for CharBlocks and strings
Use new formatting and fix usage of std::forward<>()
Use forward_list rather than vector to save strings
Original-commit: flang-compiler/f18@8ea478420f
Reviewed-on: https://github.com/flang-compiler/f18/pull/444
Tree-same-pre-rewrite: false
* Clause 12 semantics
Check all constraints not otherwise checked during parsing or label scope
validation, except for C1201, C1231, and C1233-5. Obvious program
requirements are also checked, except for 12.6.2.2 constant format string
validation.
Original-commit: flang-compiler/f18@e4ec343618
Reviewed-on: https://github.com/flang-compiler/f18/pull/427
