parse-tree.h, parse-tree.cc:
Add FunctionReference::ConvertToArrayElementRef() to convert a function
reference to an array element reference.
Factor out MakeArrayElementRef() to use in ConvertToArrayElementRef()
and also in converting statement functions to array element assignments.
resolve-names.cc:
Recognize references to functions and subroutines and add symbols for them.
Detect declaration conflicts from these and check `IMPLICIT NONE(EXTERNAL)`.
rewrite-parse-tree.cc:
Find function references that need to be converted and rewrite them.
Original-commit: flang-compiler/f18@e5a1e0aaef
Reviewed-on: https://github.com/flang-compiler/f18/pull/65
744427238c