#52 Avoid winrun4j build dependency (new build property)

[niol]

This patch introduces a new build property to avoid winrun4j build dependency.

--- davmail.git.orig/build.xml  2018-11-22 09:30:38.385081149 +0100
+++ davmail.git/build.xml   2018-11-22 09:38:16.152157233 +0100
@@ -93,6 +93,7 @@
         <javac srcdir="src/java" destdir="target/classes" source="9" debug="on" encoding="UTF-8"^M
                includeantruntime="false">^M
             <exclude name="davmail/exchange/auth/*Interactive*" unless="is.javafx"/>^M
+            <exclude name="davmail/service/DavService.java" if="nowindowsservice"/>^M
             <compilerarg value="--add-exports" />^M
             <compilerarg value="java.naming/com.sun.jndi.ldap=ALL-UNNAMED" />^M
             <classpath>^M
@@ -106,6 +107,7 @@
         <javac srcdir="src/java" destdir="target/classes" source="1.6" target="1.6" debug="on" encoding="UTF-8"^M
                includeantruntime="false">^M
             <exclude name="davmail/exchange/auth/*Interactive*" unless="is.javafx"/>^M
+            <exclude name="davmail/service/DavService.java" if="nowindowsservice"/>^M
             <classpath>^M
                 <path refid="classpath"/>^M
             </classpath>^M