[flang] Handle more use cases reported for issues/78797 (#79628)

I implemented legacy "token pasting" via line continuation for

  call prefix&
    &MACRO&
    &suffix(1)

in a recent patch; this patch addresses the related cases

  call prefix&
    &MACRO&
    &(1)

and

  call &
    &MACRO&
    &suffix(1)

Fixes the latest https://github.com/llvm/llvm-project/issues/79590.