Use the 'maven.compile.source' property instead of a hard-wired version number.
Use the 'maven.compile.source' property instead of a hard-wired version number.

git-svn-id: 897293da6115b9493049ecf64199cf2f9a0ac287@1418300 13f79535-47bb-0310-9956-ffa450edef68

UlrichColby/httpcomponents-client,apache/httpcomponents-client,ok2c/httpclient