CompilerType: Add ability to retrieve an integral template argument

Summary:
Despite it's name, GetTemplateArgument was only really working for Type
template arguments. This adds the ability to retrieve integral arguments
as well (which I've needed for the std::bitset data formatter).

I've done this by splitting the function into three pieces. The idea is
that one first calls GetTemplateArgumentKind (first function) to
determine the what kind of a parameter this is. Based on that, one can
then use specialized functions to retrieve the correct value. Currently,
I only implement two of these: GetTypeTemplateArgument and
GetIntegralTemplateArgument.

Reviewers: jingham, clayborg

Subscribers: lldb-commits

Differential Revision: https://reviews.llvm.org/D39844

llvm-svn: 318040
diff --git a/lldb/source/Plugins/Language/CPlusPlus/LibCxxVector.cpp b/lldb/source/Plugins/Language/CPlusPlus/LibCxxVector.cpp
index 6f601c9..7111306 100644
--- a/lldb/source/Plugins/Language/CPlusPlus/LibCxxVector.cpp
+++ b/lldb/source/Plugins/Language/CPlusPlus/LibCxxVector.cpp
@@ -290,8 +290,7 @@
   CompilerType type = valobj_sp->GetCompilerType();
   if (!type.IsValid() || type.GetNumTemplateArguments() == 0)
     return nullptr;
-  TemplateArgumentKind kind;
-  CompilerType arg_type = type.GetTemplateArgument(0, kind);
+  CompilerType arg_type = type.GetTypeTemplateArgument(0);
   if (arg_type.GetTypeName() == ConstString("bool"))
     return new LibcxxVectorBoolSyntheticFrontEnd(valobj_sp);
   return new LibcxxStdVectorSyntheticFrontEnd(valobj_sp);