for regoff_t, it's impossible to match on 64-bit archs because glibc defined the type in a non-conforming way. however this change makes the type match on 32-bit archs.
to deal with the fact that the public headers may be used with pre-c99 compilers, __restrict is used in place of restrict, and defined appropriately for any supported compiler. we also avoid the form [restrict] since older versions of gcc rejected it due to a bug in the original c99 standard, and instead use the form *restrict.