factor: fix infinite loop on 32 bit powerpc

Both Debian and Ubuntu builds of coreutils 8.20 hang while running the
test suite on powerpc, which is reproducible using 'factor 122'.

This turns out to be somewhat related to http://bugs.gnu.org/12754,
but not quite the same.  uintmax_t is 64 bits, but the cntlzw
instruction takes 32-bit operands, and the cntlzd option is only
available on 64-bit hardware.

* src/longlong.h: Add an _LP64 check around the PPC64 code,
so that this falls back to the C implementations.
* NEWS: Mention the fix.

NEWS

@@ -22,6 +22,9 @@ GNU coreutils NEWS                                    -*- outline -*-
   another range.  Before, "echo 123|cut --output-delim=: -b2-,3" would print
   "2:3".  Now it prints "23".  [bug introduced in 5.3.0]
 
+  factor no longer loops infinitely on 32 bit powerpc systems.
+  [bug introduced in coreutils-8.20]
+
   install -m M SOURCE DEST no longer has a race condition where DEST's
   permissions are temporarily derived from SOURCE instead of from M.
 

src/longlong.h

@@ -1398,7 +1398,7 @@ extern UWtype __MPN(udiv_qrnnd) (UWtype *, UWtype, UWtype, UWtype);
 
 /* We should test _IBMR2 here when we add assembly support for the system
    vendor compilers.  */
-#if HAVE_HOST_CPU_FAMILY_powerpc && W_TYPE_SIZE == 64
+#if HAVE_HOST_CPU_FAMILY_powerpc && W_TYPE_SIZE == 64 && defined (_LP64)
 #if !defined (_LONG_LONG_LIMB)
 /* _LONG_LONG_LIMB is ABI=mode32 where adde operates on 32-bit values.  So
    use adde etc only when not _LONG_LONG_LIMB.  */