Further fixes when thiscall is the default for methods.

The previous patches tried to deduce the correct function type. I now realize
this is not possible in general. Consider

class foo {
    template <typename T> static void bar(T v);
};
extern template void foo::bar(const void *);

We will only know that bar is static after a lookup, so we have to handle this
in the template instantiation code.

This patch reverts my previous two changes (but not the tests) and instead
handles the issue in DeduceTemplateArguments.

llvm-svn: 195154
diff --git a/clang/test/SemaCXX/decl-microsoft-call-conv.cpp b/clang/test/SemaCXX/decl-microsoft-call-conv.cpp
index e47a5c2..a1a6d0b2 100644
--- a/clang/test/SemaCXX/decl-microsoft-call-conv.cpp
+++ b/clang/test/SemaCXX/decl-microsoft-call-conv.cpp
@@ -176,3 +176,10 @@
   void bah() {}
   void baz() { zed(bah); }
 }
+
+namespace test4 {
+  class foo {
+    template <typename T> static void bar(T v);
+  };
+  extern template void foo::bar(const void *);
+}