This commit rearranges the internal header files.
"src/guestfs-internal.h" is just for the library, as before.
"src/guestfs-internal-frontend.h" is for use by all library, bindings,
tools C code, but NOT the daemon.
"src/guestfs-internal-all.h" is for use by all C code including the
daemon.
This is just code motion, but it has some important consequences:
(1) We can use the CLEANUP_* macros in bindings and tools code.
(2) We can get rid of TMP_TEMPLATE_ON_STACK.
(3) We will (in future) be able to stop bindings and tools code from
using the safe_* allocation functions (which are NOT safe to use
outside the library alone).