[IRInterpreter] Fix misevaluation of interpretation expressions with `urem`.

Scalar::MakeUnsigned was implemented incorrectly so it didn't
really change the sign of the type (leaving signed types signed).
This showed up as a misevaluation when IR-interpreting urem but
it's likely to arise in other contexts.

This commit fixes the definition, and adds a test to make
sure this won't regress in future (hopefully).

Fixes rdar://problem/42038760 and LLVM PR38076

Differential Revision:  https://reviews.llvm.org/D49155

llvm-svn: 336872
diff --git a/lldb/source/Core/Scalar.cpp b/lldb/source/Core/Scalar.cpp
index 72108c4..6a71869 100644
--- a/lldb/source/Core/Scalar.cpp
+++ b/lldb/source/Core/Scalar.cpp
@@ -1184,38 +1184,38 @@
   case e_void:
     break;
   case e_sint:
-    success = true;
-    break;
-  case e_uint:
     m_type = e_uint;
     success = true;
     break;
-  case e_slong:
+  case e_uint:
     success = true;
     break;
-  case e_ulong:
+  case e_slong:
     m_type = e_ulong;
     success = true;
     break;
-  case e_slonglong:
+  case e_ulong:
     success = true;
     break;
-  case e_ulonglong:
+  case e_slonglong:
     m_type = e_ulonglong;
     success = true;
     break;
-  case e_sint128:
+  case e_ulonglong:
     success = true;
     break;
-  case e_uint128:
+  case e_sint128:
     m_type = e_uint128;
     success = true;
     break;
+  case e_uint128:
+    success = true;
+    break;
   case e_sint256:
+    m_type = e_uint256;
     success = true;
     break;
   case e_uint256:
-    m_type = e_uint256;
     success = true;
     break;
   case e_float: