Drop "-Wunsafe-loop-optimizations".

It warns about totally sensible things done in intel_decode.c.  I've
never seen this warn do anything useful, and apparently I was the one
to introduce it when I added the giant pile of warning flags back in
2008.

Reviewed-by: Ben Widawsky <ben@bwidawsk.net>
diff --git a/configure.ac b/configure.ac
index 09fed53..3eaec74 100644
--- a/configure.ac
+++ b/configure.ac
@@ -133,7 +133,7 @@
 -Wpointer-arith -Wwrite-strings -Wstrict-prototypes \
 -Wmissing-prototypes -Wmissing-declarations -Wnested-externs \
 -Wpacked -Wswitch-enum -Wmissing-format-attribute \
--Wstrict-aliasing=2 -Winit-self -Wunsafe-loop-optimizations \
+-Wstrict-aliasing=2 -Winit-self \
 -Wdeclaration-after-statement -Wold-style-definition \
 -Wno-missing-field-initializers -Wno-unused-parameter \
 -Wno-attributes -Wno-long-long -Winline"