Merge of branch 'hex-float'.
- Add support in byterun/floats.c for conversions between floats and strings in hex notation. We cannot rely on the C standard library here because Microsoft consistently fails at supporting hex notation as standardized in C99. Instead, the conversions are implemented from scratch.
- Add support in the lexer so that hex float literals are recognized in OCaml sources.
- Add support in formats. The ISO C99 format letters for hex floats are %a and %A, but %a is already taken. I chose %h and %H, which are rejected today as bad formats (hence no backward incompatibility) and don't mean anything in C either (h is a modifier, not a format letter).
- Add support in printf. All the trimmings are there in the implementation of %h and %H, including sign modifier and fixed precision.
- Benoit Vaugon contributed support in scanf.
Resolved conflicts:
boot/ocamlc
boot/ocamldep
boot/ocamllex
parsing/lexer.mll