_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.
rename SYSCALL_NOLABEL as CALLSYS_ERROR (for consistency with CALLSYS_NOERROR
now in asm.h), and implement it using CALLSYS_NOERROR.
reimplement SYSCALL, RSYSCALL, and PSEUDO to use the appropriate macros.
implement SYSCALL_NOERROR and RSYSCALL_NOERROR to do the same thing as
SYSCALL and RSYSCALL, but without the error checking/handling.
thorpej