Hurd bug fix

[Jeffrey A Law]

  In message < 199903110840.JAA18730@landau.wins.uva.nl >you write:
  > STANDARD_INCLUDE_DIR defines where the compiler looks for includes at
  > runtime.  SYSTEM_HEADER_DIR is used at build time (in gcc/Makefile)
  > to check if there is a limits.h provided by the system
Ugh!


  > The thing
  > needs to be redisigned anyway since right now LIMITS_H_TEST tests for
  > the existence of the file on the host where it should check the target
  > instead.
Err, no, SYSTEM_HEADER_DIR is redefined to $(tooldir)/sys-include when
cross-compiling.


  > Note that the same thing is happening for some of the MIPS targets
  > (for example see gcc/config/mips/bsd-4.h and gcc/config/mips/t-bsd).
That's good to know, but it doesn't necessarily make it correct.

jeff