LDC: Add -boundscheck=off -singleobj
LDC: Add -boundscheck=off -singleobj

The other two D compilers already had bounds checking disabled.

-singleobj leads to better optimization potential in the "all-at-once"
compilation model, as the compiler is not forced to create separate
object files for each source file (it's the default when using the ldmd2
driver).
artemalive/DigitalWhip,artemalive/DigitalWhip,artemalive/DigitalWhip,artemalive/DigitalWhip