Replace 'ap' with 'up' suffix in variable names. (NFC)

The `ap` suffix is a remnant of lldb's former use of auto pointers,
before they got deprecated. Although all their uses were replaced by
unique pointers, some variables still carried the suffix.

In r353795 I removed another auto_ptr remnant, namely redundant calls to
::get for unique_pointers. Jim justly noted that this is a good
opportunity to clean up the variable names as well.

I went over all the changes to ensure my find-and-replace didn't have
any undesired side-effects. I hope I didn't miss any, but if you end up
at this commit doing a git blame on a weirdly named variable, please
know that the change was unintentional.

llvm-svn: 353912
diff --git a/lldb/source/Plugins/Process/Utility/HistoryThread.cpp b/lldb/source/Plugins/Process/Utility/HistoryThread.cpp
index a2b71b5..23f6077 100644
--- a/lldb/source/Plugins/Process/Utility/HistoryThread.cpp
+++ b/lldb/source/Plugins/Process/Utility/HistoryThread.cpp
@@ -32,7 +32,7 @@
       m_extended_unwind_token(LLDB_INVALID_ADDRESS), m_queue_name(),
       m_thread_name(), m_originating_unique_thread_id(tid),
       m_queue_id(LLDB_INVALID_QUEUE_ID) {
-  m_unwinder_ap.reset(new HistoryUnwind(*this, pcs, stop_id_is_valid));
+  m_unwinder_up.reset(new HistoryUnwind(*this, pcs, stop_id_is_valid));
   Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_OBJECT));
   if (log)
     log->Printf("%p HistoryThread::HistoryThread", static_cast<void *>(this));
@@ -59,7 +59,7 @@
 
 lldb::RegisterContextSP
 HistoryThread::CreateRegisterContextForFrame(StackFrame *frame) {
-  return m_unwinder_ap->CreateRegisterContextForFrame(frame);
+  return m_unwinder_up->CreateRegisterContextForFrame(frame);
 }
 
 lldb::StackFrameListSP HistoryThread::GetStackFrameList() {