PR#6075: avoid using unsafe   C library functions (strcpy, strcat, sprintf).
An ISO C99-compliant C compiler and standard library is now assumed.
(Plus special exceptions for MSVC.)  In particular, emulation code for
64-bit integer arithmetic was removed, the C compiler must support a
64-bit integer type.


git-svn-id: http://caml.inria.fr/svn/ocaml/trunk@14607 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02