The setting for R was previous omitted in Sys.runtime_parameters, since
it was only processed directly by the Hashtbl module and not stored in
the runtime. Option R is now processed in caml_parase_ocamlrunparam and
stored to be accessed and updated via new primitives for the Hashtbl
module.

Co-authored-by: David Allsopp <david.allsopp@metastack.com>

Consistency - options displayed in alphabetical order with the uppercase
letter appearing before the lowercase letter

When linking an executable, allows to set default to OCAMLRUNPARAM
values. This new OCAMLRUNPARAM string is accessible using the
"caml_executable_ocamlrunparam" symbol or is embedded in a bytecode
section.

Co-authored-by: Antonin Décimo <antonin@tarides.com>

The test programs in the run after the prefix has been renamed are
compiled with `-set-runtime-default R`, and the test program verifies
that Hashtbl.is_randomized returns the expected value.

In bytecode startup, defer allocating memory until after the bytecode
image has been loaded as far as possible.

The runtime's pooling mode has a slight Catch-22 problem for ocamlrun
when enabled using -set-runtime-default. Opening the bytecode file and
reading the ORUN section requires the memory subsystem.

In this revised version, caml_main in bytecode is particularly careful
to track exactly what will have been allocated prior to reading the ORUN
section and if ORUN requires the system to start pooling mode, the
runtime now takes temporary malloc'd copies of everything which has been
made so far so that it can be safely copied with a caml_stat_alloc
_after_ pooling mode has been enabled.