[svn r112] Fixed 'case 1,2,3:' style case statements.

Fixed a bunch of bugs with return/break/continue in loops.
Fixed support for the DMDFE hidden implicit return value variable. This can be needed for some foreach statements where the loop body is converted to a nested delegate, but also possibly returns from the function.
Added std.math to phobos.
Added AA runtime support code, done ground work for implementing AAs.
Several other bugfixes.

test/aa1.d

@@ -0,0 +1,6 @@
+module aa1;
+
+void main()
+{
+    int[int] aai;
+}

test/bug70.d

@@ -0,0 +1,9 @@
+module bug70;
+
+void main()
+{
+    for (;false;)
+    {
+        break;
+    }
+}

test/bug71.d

@@ -0,0 +1,20 @@
+module bug71;
+
+void main()
+{
+    static TypeInfo skipCI(TypeInfo valti)
+    {
+      while (1)
+      {
+    if (valti.classinfo.name.length == 18 &&
+        valti.classinfo.name[9..18] == "Invariant")
+        valti = (cast(TypeInfo_Invariant)valti).next;
+    else if (valti.classinfo.name.length == 14 &&
+        valti.classinfo.name[9..14] == "Const")
+        valti = (cast(TypeInfo_Const)valti).next;
+    else
+        break;
+      }
+      return valti;
+    }
+}

test/bug72.d

@@ -0,0 +1,8 @@
+module bug72;
+
+void main()
+{
+    char c = void;
+    int i = void;
+    c += i;
+}

test/bug73.d

@@ -0,0 +1,14 @@
+int find(char[] s, dchar c)
+{
+    // c is a universal character
+    foreach (int i, dchar c2; s)
+    {
+    if (c == c2)
+        return i;
+    }
+    return -1;
+}
+
+void main()
+{
+}

test/switch2.d

@@ -0,0 +1,12 @@
+module switch2;
+
+void main()
+{
+    int i = 2;
+    switch(i)
+    {
+    case 0: assert(0);
+    case 1,2: printf("hello world\n"); break;
+    default: assert(0);
+    }
+}