Use Kernel#caller_locations (2.x) (#1491)

Ruby 2.x+ has a built-in implementation of `caller_locations`,
which differs slightly from the Sinatra implementation of the same name.
This removes the customized implementation in favor of the system one

Co-authored-by: Jordan Owens <jkowens@gmail.com>

lib/sinatra/base.rb

@@ -900,9 +900,10 @@ module Sinatra
     end
 
     def compile_block_template(template, options, &body)
-      caller = settings.caller_locations.first
-      path = options[:path] || caller[0]
-      line = options[:line] || caller[1]
+      first_location = caller_locations.first
+      path, line = first_location.path, first_location.lineno
+      path = options[:path] || path
+      line = options[:line] || line
       template.new(path, line.to_i, options, &body)
     end
   end
@@ -1553,12 +1554,6 @@ module Sinatra
         cleaned_caller(1).flatten
       end
 
-      # Like caller_files, but containing Arrays rather than strings with the
-      # first element being the file, and the second being the line.
-      def caller_locations
-        cleaned_caller 2
-      end
-
       private
 
       # Starts the server by running the Rack Handler.

sinatra-contrib/lib/sinatra/namespace.rb

@@ -299,8 +299,9 @@ module Sinatra
       end
 
       def template(name, &block)
-        filename, line = caller_locations.first
-        templates[name] = [block, filename, line.to_i]
+        first_location = caller_locations.first
+        filename, line = first_location.path, first_location.lineno
+        templates[name] = [block, filename, line]
       end
 
       def layout(name=:layout, &block)