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/Darwin/NativeThreadDarwin.cpp b/lldb/source/Plugins/Process/Darwin/NativeThreadDarwin.cpp
index a1979c5..bcd6d8c 100644
--- a/lldb/source/Plugins/Process/Darwin/NativeThreadDarwin.cpp
+++ b/lldb/source/Plugins/Process/Darwin/NativeThreadDarwin.cpp
@@ -138,7 +138,7 @@
     // Allow the arch specific protocol to process (MachException::Data &)exc
     // first before possible reassignment of m_stop_exception with exc. See
     // also MachThread::GetStopException().
-    bool handled = m_arch_ap->NotifyException(exc);
+    bool handled = m_arch_up->NotifyException(exc);
 
     if (m_stop_exception.IsValid())
     {
@@ -175,7 +175,7 @@
     }
     else
     {
-        if (m_arch_ap->StepNotComplete())
+        if (m_arch_up->StepNotComplete())
         {
             step_more = true;
             return false;
@@ -217,7 +217,7 @@
 
     // When this method gets called, the process state is still in the state it
     // was in while running so we can act accordingly.
-    m_arch_ap->ThreadDidStop();
+    m_arch_up->ThreadDidStop();
 
 
     // We may have suspended this thread so the primary thread could step