kernel: Make chflags syscalls argument types consistent with userland.

kernel: Make chflags syscalls argument types consistent with userland.

 There was an inconsistency between userland and syscalls argument types
 that was inherited after initial fork.  Adjust prototypes to use u_long
 and add missing const char* too.  Rerun sysent.  Change tmpfs/dirfs to
 use u_int for flags since mask for superuser changeable flags is
 SF_SETTABLE 0xffff0000 (most fs use uint32_t), adjust mksubr script.
 Remove no longer needed (u_long) casts I could find elsewhere.

 While there, adjust unistd.h prototypes to use generic types too.