Fix the required args count for variadic blocks.

We were emitting calls to blocks as if all arguments were
required --- i.e. with signature (A,B,C,D,...) rather than
(A,B,...).  This patch fixes that and accounts for the
implicit block-context argument as a required argument.
In addition, this patch changes the function type under which
we call unprototyped functions on platforms like x86-64 that
guarantee compatibility of variadic functions with unprototyped
function types;  previously we would always call such functions
under the LLVM type T (...)*, but now we will call them under
the type T (A,B,C,D,...)*.  This last change should have no
material effect except for making the type conventions more
explicit;  it was a side-effect of the most convenient implementation.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@169588 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/CGCall.h b/lib/CodeGen/CGCall.h
index 4713db7..b0b136d 100644
--- a/lib/CodeGen/CGCall.h
+++ b/lib/CodeGen/CGCall.h
@@ -134,7 +134,7 @@
     }
 
     bool allowsOptionalArgs() const { return NumRequired != ~0U; }
-    bool getNumRequiredArgs() const {
+    unsigned getNumRequiredArgs() const {
       assert(allowsOptionalArgs());
       return NumRequired;
     }