File read-able check should ignore file creation flags

[yabberyabber]

currently you'll get an error when you try to read from a file which was opened using a mode like O_RDONLY | O_CREATE, because the check for "is this file read-able" checks for ((flags | O_RDWR) || flags == 0).

With this change, all we check for is that the file was not opened with O_WRONLY.

Flags like O_CREATE and O_TRUNCATE don't actually impact the access that a process can have to an open file. When checking whether a process has read access, all that really matters is that the file isn't opened with O_WRONLY.