Fix the SYSCALLS.TXT documentation and remove a dead script.

We use the system call constants from the kernel header files now,
so there's no need to check that they've been correctly transcribed
into SYSCALLS.TXT.

This is a work in progress. I've added TODOs to SYSCALLS.TXT explaining
what's left to do.

Change-Id: I3b86acfe7f84b4da1c802ee5a4ef13a2e83e7939
2 files changed