Changed premake.lua to work with mingw.

Implemented array operations, not perfect but ok for tonight. closes #89

tests/mini/arrayops1.d

@@ -0,0 +1,17 @@
+extern(C) int printf(char*, ...);
+
+void main()
+{
+    int[3] a = [1, 2, 3];
+    int[3] b = [4, 5, 6];
+    int[3] c;
+
+    c[] = a[] + b[];
+
+    printf("c.ptr = %p\n", c.ptr);
+    printf("c.length = %lu\n", c.length);
+
+    assert(c[0] == 5);
+    assert(c[1] == 7);
+    assert(c[2] == 9);
+}