Some calling convention work for x86-64: - Implement x86-64 extern(C), hopefully correctly. - Tried to be a bit smarter about extern(D) while I was there. Interestingly, this code seems to be generating more efficient code than gcc and llvm-gcc in some edge cases, like returning a `{ [7 x i8] }` loaded from a stack slot from an extern(C) function. (gcc generates 7 1-byte loads, while this code generates a 4-byte, a 2-byte and a 1-byte load) I also added some changes to make sure structs being returned from functions or passed in as parameters are stored in memory where the rest of the backend seems to expect them to be. These should be removed when support for first-class aggregates improves.

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