Fixed warning that failed build in previous patchset.
Here's rebased patch:
v23-0001-toaster-interface.patch - PluggableTOAST API interface with reference (original) TOAST mechanics - new API is introduced but
reference TOAST is still left unchanged;
v23-0002-toaster-default.patch - Default TOAST mechanics is re-implemented using TOAST API and is plugged in as Default Toaster; v23-0003-toaster-docs.patch - PluggableTOAST API documentation package
For TOAST API explanation please check /src/backend/access/README.toastapi