Followup to fix for https://issues.apache.org/bugzilla/show_bug.cgi?id=56829
Be more strict with executable filename on Windows (s/java/java.exe/).

When file name extension is not specified, Windows uses the value of %PATHEXT% environment variable to enumerate applicable filename extensions.
On my Windows 7 its value is ".COM;.EXE;.BAT;.CMD;.VBS;.VBE;.JS;.JSE;.WSF;.WSH;.MSC".
I think it is a bit more secure if filename is specified explicitly.

There shall be no observable difference in behaviour, as .EXE is at the start of the PATHEXT list (e.g. earlier than .BAT).

git-svn-id: https://svn.apache.org/repos/asf/tomcat/trunk@1617456 13f79535-47bb-0310-9956-ffa450edef68