_ASM_LABEL(cerror) and _ASM_LABEL(curbrk) to _C_LABEL(__cerror) and
_C_LABEL(__curbrk) (or their respective architecture-specific equivalents) to
avoid possible name clashes with identifiers used in user applications.
* Do the same for minbrk on all architectures to avoid a GCC-specific (and
on ELF architectures effectively useless) symbol reference renaming in MI code.
SYSTRAP(x): Expands to the code used to call syscall x.
This is used to simplify other macros.
SYSCALL_NOERROR(x): Like SYSCALL except that "x" is a syscall
that can never fail.
RSYSCALL_NOERROR(x): Like RSYSCALL except that "x" is a syscall
that can never fail.
