Fix Backtrace from collapsing too many recursive frames

Recursing through method_missing, be sure to check the sending name
(Location#name) when deciding to collapse the frame, otherwise the
backtrace is super confusing because it lists method_missing for many
different methods.

kernel/common/backtrace.rb

@@ -51,15 +51,17 @@ def show(sep="\n")
     lines = []
     last_method = nil
     last_line = nil
+    last_name = nil
     times = 0
 
     @locations.each do |loc|
-      if loc.method == last_method and loc.line == last_line
+      if loc.name == last_name and loc.method == last_method and loc.line == last_line
         times += 1
       else
         lines.last[-1] = times if lines.size > 0
         last_method = loc.method
         last_line = loc.line
+        last_name = loc.name
 
         str = loc.describe
         max = str.size if str.size > max