Allocate Expr on a custom address to be able to release memory.
Allocate Expr on a custom address to be able to release memory.

We now use operator new with placement to memory explicit
allocated in the routine (rather than the ASTContext) so
that we can release this memory at the end of the function.
The memory is allocated via a vector of object large enough
to hold the OpaqueExprRef.

marsupial/cling,perovic/cling,perovic/cling,root-mirror/cling,perovic/cling,root-mirror/cling,root-mirror/cling,root-mirror/cling,marsupial/cling,marsupial/cling,perovic/cling,root-mirror/cling,karies/cling,karies/cling,karies/cling,marsupial/cling,perovic/cling,marsupial/cling,karies/cling,root-mirror/cling,marsupial/cling,karies/cling,karies/cling