RFR (S): 8241947: Minor comment fixes for system property handling

[Langer, Christoph]

Hi,

please review a small fix that updates two comments.

The first one, in make/autoconf/spec.gmk.in, is probably quite old. It talks about handling of a property "vm.vendor" in VersionProps.java.template. However, there is no property "vm.vendor", it must rather be "java.vendor". I stumbled over that when looking at the change of JDK-4947890 (Minimize JNI upcalls in system-properties initialization).

The second one is the code comment attached to "private static Properties props;" in java.lang.System. After JDK-8197927 (Allow the system property `java.vendor.version` to be undefined), "java.vendor.version" can be undefined, so this should be reflected in the comment. I also took the liberty to remove an unneeded import statement.

Bug: https://bugs.openjdk.java.net/browse/JDK-8241947
Webrev: http://cr.openjdk.java.net/~clanger/webrevs/8241947.0/

Thanks
Christoph