keyletters F, I, S, W. Remove unused keyletter V. Surround
signature argnames with angle-brackets for use as word delimiters,
and to induce syntax errors for any args not handled. Split
multi-echo echoes and comment each stage.
* sysdeps/unix/common/syscalls.list: Refine & correct signatures.
* sysdeps/unix/inet/syscalls.list: Likewise.
* sysdeps/unix/mman/syscalls.list: Likewise.
* sysdeps/unix/syscalls.list: Likewise.
* sysdeps/unix/sysv/linux/ia64/syscalls.list: Likewise.
* sysdeps/unix/sysv/linux/mips/syscalls.list: Likewise.
* sysdeps/unix/sysv/linux/syscalls.list: Likewise.
* sysdeps/unix/sysv/syscalls.list: Likewise.
* sysdeps/unix/sysv/linux/powerpc/syscalls.list
* sysdeps/generic/bp-thunks.h: Replace generic thunk definitions
with list of #include files.
* sysdeps/unix/make-syscalls.sh: Handle new arg signature
keyletters a, b, B, f, n, N, P, v, V. Fixup some indentation.
Don't generate BP thunk if `V' appears in signature.
Generate thunks with complete bounds checks.
* sysdeps/unix/syscalls.list: Refine signatures using new keyletters.
* sysdeps/unix/inet/syscalls.list: Likewise.
* sysdeps/unix/mman/syscalls.list: Likewise.
* sysdeps/unix/sysv/linux/syscalls.list: Likewise.
* sysdeps/unix/sysv/linux/ia64/syscalls.list: Likewise.
* sysdeps/unix/sysv/linux/mips/syscalls.list: Likewise.
* sysdeps/unix/sysv/linux/powerpc/syscalls.list: Likewise.