Clarify that stdlib experiments with annotations are not encouraged.

pep-0008.txt

@@ -1257,10 +1257,11 @@ annotations are changing.
 - The experimentation with annotation styles that was recommended
   previously in this PEP is no longer encouraged.
 
-- However, experiments within the rules of PEP 484 are now encouraged.
-  For example, marking up a large library with PEP 484 style type
-  annotations, reviewing how easy it was to add those annotations, and
-  observing whether their presence increases code understandabilty.
+- However, outside the stdlib, experiments within the rules of PEP 484
+  are now encouraged.  For example, marking up a large third party
+  library or application with PEP 484 style type annotations,
+  reviewing how easy it was to add those annotations, and observing
+  whether their presence increases code understandabilty.
 
 - The Python standard library should be conservative in adopting such
   annotations, but their use is allowed for new code and for big
@@ -1280,12 +1281,12 @@ annotations are changing.
   checking and should not alter their behavior based on annotations.
 
 - Users who don't want to use type checkers are free to ignore them.
-  However, it is expected that users of library packages may want to
-  run type checkers over those library packages.  For this purpose PEP
-  484 recommends the use of stub files: .pyi files that are read by
-  the type checker in preference of the corresponding .py files.  Stub
-  files can be distributed with a library, or separately (with the
-  library author's permission) through the _typeshed_ repo [5]_.
+  However, it is expected that users of third party library packages
+  may want to run type checkers over those packages.  For this purpose
+  PEP 484 recommends the use of stub files: .pyi files that are read
+  by the type checker in preference of the corresponding .py files.
+  Stub files can be distributed with a library, or separately (with
+  the library author's permission) through the typeshed repo [5]_.
 
 - For code that needs to be backwards compatible, function annotations
   can be added in the form of comments.  Basically, this Python 3 annotation::
@@ -1301,7 +1302,7 @@ annotations are changing.
         """Embezzle funds from account using fake receipts."""
         <code goes here>
 
-  The _mypy_ type checker [6]_ currently supports this syntax, and other
+  The mypy type checker [6]_ currently supports this syntax, and other
   type checkers are encouraged to adopt it.