[flang] Implement !DIR$ UNROLL [N] (#123331)

This patch implements support for the UNROLL directive to control how
many times a loop should be unrolled.
It must be placed immediately before a `DO LOOP` and applies only to the
loop that follows. N is an integer that specifying the unrolling factor.
This is done by adding an attribute to the branch into the loop in LLVM
to indicate that the loop should unrolled.
The code pushed to support the directive `VECTOR ALWAYS` has been
modified to take account of the fact that several directives can be used
before a `DO LOOP`.

0 files changed, 0 insertions, 0 deletions