Add NEWS/UPGRADING for previous change

Author: nikic

NEWS

@@ -26,6 +26,8 @@ PHP                                                                        NEWS
     (srgoogleguy, Gustavo)
   . Implemented FR #60738 (Allow 'set_error_handler' to handle NULL).
     (Laruence, Nikita Popov)
+  . Return previous handler when passing NULL to set_error_handler and
+    set_exception_handler. (Nikita Popov)
   . Added optional second argument for assert() to specify custom message. Patch
     by Lonny Kapelushnik (lonny@lonnylot.com). (Lars)
 

UPGRADING

@@ -107,6 +107,10 @@ PHP X.Y UPGRADE NOTES
   but that predated the existence of E_DEPRECATED.
 - php_logo_guid(), php_egg_logo_guid(), php_real_logo_guid() and 
   zend_logo_guid() have been removed
+- set_error_handler(NULL) can now be used to reset the error handler.
+  Furthermore both set_error_handler(NULL) and set_exception_handler(NULL) will
+  now return the previously defined error/exception handler. Previously
+  bool(true) was returned.
 
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 5. New Functions