POSIX: make readv() and writev() conform to IEEE Std 1003.1-2001

The standardized version of readv() and writev() take an int as the third
parameter. Arguably a size_t makes more sense, but the standardization bodies
decided otherwise.

The non-standard functions of readv_pos() and writev_pos() have been updated
for consistency. The corresponding _kern_readv() and _kern_writev() internal
functions continue to take the size_t parameter.

The ABI will not change, even though on 64 bit machines the size of the count
parameter will change from 8 to 4 bytes.

The actual use will be slightly different. Like with the size_t argument type,
it will not be possible to give a count lower than 0. If the value is less than
0, then the B_BAD_VALUE/EINVAL error will be set.

Change-Id: I949c8ed67dbc0b4e209768cbdee554c929fc242e
Reviewed-on: https://review.haiku-os.org/c/haiku/+/3770
Reviewed-by: Jérôme Duval <jerome.duval@gmail.com>

Beginnings of a new, better portable FS shell with Haiku FS interface.
Doesn't do anything ATM, but already provides the required system
interface (VFS, caches, POSIX functions).


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@20859 a95241bf-73f2-0310-859d-f6bbb57e9c96

Beginnings of a new, better portable FS shell with Haiku FS interface.
Doesn't do anything ATM, but already provides the required system
interface (VFS, caches, POSIX functions).


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@20859 a95241bf-73f2-0310-859d-f6bbb57e9c96