Note that this change disables compiling and running the haskell bindtests. The
haskell bindings do not implement optargs, and adding optargs to test0 causes
that method not to be bound in the haskell bindings. This prevents the haskell
bindtests from compiling. These should be re-enabled when optargs are
implemented.

The BufferIn argument turns into various things:

 in C      const char *, size_t parameter pair

 in XDR    an opaque<> type (instead of string) which allows \0 chars

 in other bindings
           mostly just a string, since most languages except for C
           permit strings to contain any 8 bit data

truncate, truncate_size: Used to truncate files to a particular
size, or to zero bytes.

mkdir_mode: Like mkdir but allows you to also specify the
initial permissions for the new directory.

utimens: Set timestamp on a file with nanosecond accuracy.

lchown: Corresponding to lchown(2) syscall (we already have chown).

The implementation is complicated by the fact that we had to
add an Int64 parameter type to the generator.