[flang] Lower allocate and deallocate statements

This patch add the lowering for the allocate
and the deallocate statements.

This patch is part of the upstreaming effort from fir-dev branch.

Reviewed By: PeteSteinfeld

Differential Revision: https://reviews.llvm.org/D121146

Co-authored-by: Eric Schweitz <eschweitz@nvidia.com>
Co-authored-by: Jean Perier <jperier@nvidia.com>
Co-authored-by: V Donaldson <vdonaldson@nvidia.com>

flang/include/flang/Lower/Allocatable.h

@@ -26,13 +26,26 @@ namespace fir {
 class MutableBoxValue;
 } // namespace fir
 
+namespace Fortran::parser {
+struct AllocateStmt;
+struct DeallocateStmt;
+} // namespace Fortran::parser
+
 namespace Fortran::lower {
 class AbstractConverter;
 
 namespace pft {
 struct Variable;
 }
 
+/// Lower an allocate statement to fir.
+void genAllocateStmt(Fortran::lower::AbstractConverter &,
+                     const Fortran::parser::AllocateStmt &, mlir::Location);
+
+/// Lower a deallocate statement to fir.
+void genDeallocateStmt(Fortran::lower::AbstractConverter &,
+                       const Fortran::parser::DeallocateStmt &, mlir::Location);
+
 /// Create a MutableBoxValue for an allocatable or pointer entity.
 /// If the variables is a local variable that is not a dummy, it will be
 /// initialized to unallocated/disassociated status.