Enable libsanitizer just on x86 linux for now

This patch builds libsanitizer only on x86_64 and i?86 linux targets
for now.  I guess The build can be enabled on other targets when they
are ready.

ChangeLog:

	* configure.ac: Enable libsanitizer just on x86 linux for now.
	* configure: Re-generate.

From-SVN: r193478