ob-ocaml.el: Make sure a value was extracted before printing

* lisp/ob-ocaml.el (org-babel-execute:ocaml): Do not try to print
a value if either the type or the value could not be extracted from
the toplevel.
Merge branch 'master' into omm
lisp/omm.el: Rename and refactor three functions

* lisp/omm.el (omm-set-org-bol): Rename to `omm-calc-org-bol' and
  refactor accordingly.
(omm-set-org-eol): Rename to `omm-calc-org-eol' and refactor
  accordingly.
(omm-set-org-star): Rename to `omm-calc-org-star' and refactor
  accordingly.

Use the refactored functions in the minor-mode definition.
lisp/omm.el: Function renamed and improved

* lisp/omm.el (omm-fix-org-regexps): Function renamed.
(omm-fix-org-regexps): Function renamed and thus removed.
(omm-convert-static-to-dynamic-regexp): New function based on `omm-fix-org-regexps'.
lisp/omm.el: Fix usage of refactored function

* lisp/omm.el (define-minor-mode): Fix call to `omm-convert-static-to-dynamic-regexp'.
lisp/org.el: Fix bugs in `org-rx'

* lisp/org.el (org-rx): Correctly handle redundant "\\|" at the end of
  regexp alternatives. Fix bugs in creation of groups and shy groups.
lisp/omm.el: Regexps extracted to constants

* lisp/omm.el (omm-convert-static-to-dynamic-regexp): Regexp extracted
  from function into separate constants.
(omm-bol-regexp, omm-eol-regexp, omm-org-stars-alternatives): New
constants.
lisp/org.el: Add option 'append to org-rx

* lisp/org.el (org-rx): Add new possible value 'append to ENCLOSING
  argument.
(org-regexp-group-p): New function.

New ENCLOSING option 'append appending existing regexp groups without
enclosing them once again. Function `org-regexp-group-p' checks if a
regexp qualifies as regexp group.