Avoid "possible NPE" warning from IDE

git-svn-id: https://svn.apache.org/repos/asf/httpcomponents/httpclient/branches/4.3.x@1578433 13f79535-47bb-0310-9956-ffa450edef68
Use explicit locale with upper/lower case conversions

git-svn-id: https://svn.apache.org/repos/asf/httpcomponents/httpclient/branches/4.3.x@1578439 13f79535-47bb-0310-9956-ffa450edef68