Doc issues in assorted small jdk.* modules

The following files in the jdk/ repo has accessibility and other minor doc issues:

src/jdk.httpserver/share/classes/com/sun/net/httpserver/HttpServer.java
src/jdk.incubator.httpclient/share/classes/jdk/incubator/http/HttpResponse.java
src/jdk.net/share/classes/jdk/net/NetworkPermission.java