syscall: include complete prototype of system calls
syscall: include complete prototype of system calls

The prototypes were truncated because they were on multiple lines
of the source file.

Copied from the STD lines for these functions in
https://svn.freebsd.org/base/stable/12/sys/kern/syscalls.master

Change-Id: I618a5444f1353aabee2758c06f86ad726185d19c
Reviewed-on: https://go-review.googlesource.com/c/go/+/188077
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>

akutz/go,nawawi/go,akutz/go,CAFxX/go,akutz/go,akutz/go,akutz/go,CAFxX/go,cloudflare/go,cloudflare/go,cloudflare/go,cloudflare/go,golang/go,golang/go,CAFxX/go,golang/go,golang/go,cloudflare/go,golang/go,akutz/go,CAFxX/go,CAFxX/go,cloudflare/go,golang/go,CAFxX/go,CAFxX/go,nawawi/go,nawawi/go,nawawi/go,cloudflare/go,cloudflare/go,golang/go,nawawi/go,akutz/go,nawawi/go,CAFxX/go,nawawi/go,nawawi/go,golang/go,akutz/go