FFI: Compile VLA/VLS and large cdata allocs with default initialization.

doc/ext_ffi_semantics.html

@@ -1219,9 +1219,8 @@ suboptimal performance, especially when used in inner loops:
 <li>Vector operations.</li>
 <li>Table initializers.</li>
 <li>Initialization of nested <tt>struct</tt>/<tt>union</tt> types.</li>
-<li>Allocations of variable-length arrays or structs.</li>
-<li>Allocations of C&nbsp;types with a size &gt; 128&nbsp;bytes or an
-alignment &gt; 8&nbsp;bytes.</li>
+<li>Non-default initialization of VLA/VLS or large C&nbsp;types
+(&gt; 128&nbsp;bytes or &gt; 16 array elements.</li>
 <li>Conversions from lightuserdata to <tt>void&nbsp;*</tt>.</li>
 <li>Pointer differences for element sizes that are not a power of
 two.</li>