Standardize on VIRT_ADDR_VARIES behavior.

Otherwise, valgrind does not work on some platforms.
Problem reported by Andreas Schwab in
<http://lists.gnu.org/archive/html/emacs-devel/2011-11/msg00081.html>.
* puresize.h (pure, PURE_P): Always behave as if VIRT_ADDR_VARIES
is set, removing the need for VIRT_ADDRESS_VARIES.
(PURE_P): Use a more-efficient implementation that needs just one
comparison, not two: on x86-64 with GCC 4.6.2, this cut down the
number of instructions from 6 (xorl, cmpq, jge, xorl, cmpq, setge)
to 4 (xorl, subq, cmpq, setbe).
* alloc.c (pure): Always extern now, since that's the
VIRT_ADDR_VARIES behavior.
(PURE_POINTER_P): Use a single comparison, not two, for
consistency with the new puresize.h.
* lisp.h (PNTR_COMPARISON_TYPE): Remove; no longer needed.
* m/ibms390.h, m/intel386.h, m/template.h, s/cygwin.h, s/hpux10-20.h:
Remove VIRT_ADDR_VARIES no longer needed.

Fixes: debbugs:10042

diff --cc src/ChangeLog
index 2973ecc4b579fd2341808ed881a1c78e1ae2cfb4,17c27bc304853eb66c1d6bd72a2c934df4b525b0..7accd0d5eea68d77f77d009338a85517ed104c03
--- 1/src/ChangeLog
--- 2/src/ChangeLog
+++ b/src/ChangeLog
@@@ -1,3 -1,22 +1,23 @@@
 -      Standardize on VIRT_ADDR_VARIES behavior; otherwise, valgrind
 -      does not work on some platforms.  Problem reported by Andreas Schwab in
+ 2011-11-20  Paul Eggert  <eggert@cs.ucla.edu>
+ 
++      Standardize on VIRT_ADDR_VARIES behavior (Bug#10042).
++      Otherwise, valgrind does not work on some platforms.
++      Problem reported by Andreas Schwab in
+       <http://lists.gnu.org/archive/html/emacs-devel/2011-11/msg00081.html>.
+       * puresize.h (pure, PURE_P): Always behave as if VIRT_ADDR_VARIES
+       is set, removing the need for VIRT_ADDRESS_VARIES.
+       (PURE_P): Use a more-efficient implementation that needs just one
+       comparison, not two: on x86-64 with GCC 4.6.2, this cut down the
+       number of instructions from 6 (xorl, cmpq, jge, xorl, cmpq, setge)
+       to 4 (xorl, subq, cmpq, setbe).
+       * alloc.c (pure): Always extern now, since that's the
+       VIRT_ADDR_VARIES behavior.
+       (PURE_POINTER_P): Use a single comparison, not two, for
+       consistency with the new puresize.h.
+       * lisp.h (PNTR_COMPARISON_TYPE): Remove; no longer needed.
+       * m/ibms390.h, m/intel386.h, m/template.h, s/cygwin.h, s/hpux10-20.h:
+       Remove VIRT_ADDR_VARIES no longer needed.
+ 
  2011-11-19  Eli Zaretskii  <eliz@gnu.org>
  
        * xdisp.c (x_write_glyphs, draw_phys_cursor_glyph)