MSVC 7, 8 & 9 use the .vcproj extension

MSVC 10 & 11 use the .vcxproj extension
Apache.sln is common to all above versions

This allows proper detection and use of devenv in all these versions



git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1482041 13f79535-47bb-0310-9956-ffa450edef68