Introduce platform dependent memory setting in Parallel Package

Using suggestion from EPP mailing list: Reduce -Xmx to 1024MB on Windows
http://dev.eclipse.org/mhonarc/lists/epp-dev/msg02373.html

See bug 400004 and bug 389517 for further reference
diff --git a/packages/org.eclipse.epp.package.parallel.feature/epp.product b/packages/org.eclipse.epp.package.parallel.feature/epp.product
index 6fe922f..2af8ff1 100644
--- a/packages/org.eclipse.epp.package.parallel.feature/epp.product
+++ b/packages/org.eclipse.epp.package.parallel.feature/epp.product
@@ -18,12 +18,18 @@
       <programArgsWin>--launcher.XXMaxPermSize
 256M</programArgsWin>
       <vmArgs>-Dosgi.requiredJavaVersion=1.5
--Dhelp.lucene.tokenizer=standard
+-Dhelp.lucene.tokenizer=standard</vmArgs>
+      <vmArgsLin>-XX:MaxPermSize=256m
 -Xms512m
--Xmx2048m</vmArgs>
-      <vmArgsLin>-XX:MaxPermSize=256m</vmArgsLin>
+-Xmx2048m</vmArgsLin>
       <vmArgsMac>-XstartOnFirstThread -Dorg.eclipse.swt.internal.carbon.smallFonts
--XX:MaxPermSize=256m</vmArgsMac>
+-XX:MaxPermSize=256m
+-Xms512m
+-Xmx2048m</vmArgsMac>
+      <vmArgsSol>-Xms512m
+-Xmx2048m</vmArgsSol>
+      <vmArgsWin>-Xms512m
+-Xmx1024m</vmArgsWin>
    </launcherArgs>
 
    <windowImages i16="/org.eclipse.epp.package.parallel/eclipse.png" i32="/org.eclipse.epp.package.parallel/eclipse32.png" i48="/org.eclipse.epp.package.parallel/eclipse48.png"/>