Replace Obj.magic trick by a recursive definition
Expose parsed OCaml version
Fix Pretty module for OCaml 4.02

Pretty.gprintf uses the internal representation of format6 strings,
which has changed in OCaml 4.02. We check the version number and
extract the format string accordingly.
Safer fix for Pretty module

Thanks to Xavier Leroy.
Support gnu_inline attribute

Fixes bug where this attribute would be attached to function return
types instead of the whole decl, provoking compiler warnings.
Merge branch 'develop' into ptanal-fixes