6854244: change source/target used to compile JDK to 7

Reviewed-by: ohair

make/build.properties

@@ -60,8 +60,8 @@ full.version = ${release}-${build.number}
 bootstrap.full.version = ${bootstrap.release}-${build.number}
 
 # options for the <javac> tasks used to compile the tools
-javac.source = 5
-javac.target = 5
+javac.source = 7
+javac.target = 7
 javac.debug = true
 javac.debuglevel = source,lines
 javac.no.jdk.warnings = -XDignore.symbol.file=true