Merge pull request #447 from euanh/build-improvements

ocaml-rpc: Update to 1.5.1, remove js-of-ocaml dependency
Update xapi to 1.9.49 (memory fix)

Signed-off-by: David Scott <dave.scott@citrix.com>
Merge pull request #448 from djs55/fix-memory

Update xapi to 1.9.49 (memory fix)
configure: Tidy up distribution-type dispatch

Signed-off-by: Euan Harris <euan.harris@citrix.com>