Allow specific optimization passes to be requested from the command line. Now you can run "`ldc test.d -c -mem2reg -simplifycfg`" if you feel the urge. The -O<N> options are still supported, and are inserted in the passes list in the position where they appear on the command line. (so -simplifycfg -O1 -instcombine does the "right thing") One small change: -inline is renamed to -enable-inlining due to a naming conflict with the option to add the -inline pass. -inline now inserts the inlining pass in the position specified, not in the middle of -O<N>. (ldmd has been updated to translate -inline to -enable-inlining)

[Environment] 
DFLAGS=-I@RUNTIME_DIR@ -I@RUNTIME_DIR@/lib/common -L-L%@P%/../lib -d-version=Tango -defaultlib=@RUNTIME_AIO@ -debuglib=@RUNTIME_AIO@