Implement first D-specific optimization pass: -simplify-drtcalls. It uses the machinery of the standard -simplify-libcalls pass, but optimizes calls to the D runtime instead of calls to C libraries. At the moment, these optimizations are implemented by this pass: - Avoid the runtime call for `arr.length = newlen` if it can determine that the new length isn't longer than the old one. - Ditto for `cast(T[]) arr` if it will clearly always succeed. (e.g. if the length of the original array is zero, or if the old element size is a multiple of the new element size)

We have two different test sets. For the test drivers
you need do compile the .d files in this folder with
a Phobos D compiler.

To run the 'mini' test suite run
./runminitests

To run the DStress based tests execute
./runtest tmp-sensible-name
and then use 
./findregressions old-results new-results 
to display a list of regressions. You can
download old result files from
http://www.incasoftware.de/~kamm/ldc/reference