[lldb] Don't use __FUNCTION__ as a file name

Summary:
I saw while debugging that we call this file `ParseInternal`, which is not a very good name for our
fake expression file and also adds this unnecessary link between the way we name this function
and the other source location names we get from the expression parser. This patch is renaming
it to `<lldb-expr>` which is closer to the way Clang names its buffers, it doesn't depend on the
function name (which changes when I refactor this code) and it's easier to grep for.

Reviewers: davide

Reviewed By: davide

Subscribers: abidh, lldb-commits

Tags: #lldb

Differential Revision: https://reviews.llvm.org/D64545

llvm-svn: 365812

lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionParser.cpp

@@ -920,7 +920,7 @@ ClangExpressionParser::ParseInternal(DiagnosticManager &diagnostic_manager,
 
   if (!created_main_file) {
     std::unique_ptr<MemoryBuffer> memory_buffer =
-        MemoryBuffer::getMemBufferCopy(expr_text, __FUNCTION__);
+        MemoryBuffer::getMemBufferCopy(expr_text, "<lldb-expr>");
     source_mgr.setMainFileID(source_mgr.createFileID(std::move(memory_buffer)));
   }