Be more careful to separate build flags for the preload shared objects
as opposed to the valgrind code proper.  In particular, make sure that
-mpreferred-stack-boundary=2 does not get used for the preload shared
objects, since that can cause the stack to become misaligned and leads
to segfaults.  Modified version of a patch from Matthias Schwarzott
(zzam@gentoo.org).  Fixes #324050.

Also, fix the configure check in configure.ac for
-mpreferred-stack-boundary=2 so that it checks whether this is
allowable for 32-bit code generation even on 64-bit (x86) hosts.  This
check was wrong before now and led to 32-bit builds on 64-bit hosts
generating poorer code for speed critical helper functions (eg
helperc_LOADV32le) than on 32-bit builds on 32-bit hosts.



git-svn-id: svn://svn.valgrind.org/valgrind/trunk@14471 a5019735-40e9-0310-863c-91ae7b9d1cf9
evh__new_mem_heap: get rid of pointless conditional.  Spotted by
Coverity and Florian Krohm.


git-svn-id: svn://svn.valgrind.org/valgrind/trunk@14472 a5019735-40e9-0310-863c-91ae7b9d1cf9