RFR: 8025856 - Fix typos in the GC code

[Jesper Wilhelmsson]

Hi,

Anyone up for a really tedious review?

This change fixes about 300 typos in comments in the GC code. There should only 
be changes in comments in this change.

I had this out for review a while ago but it was a bit late in 8u20 to push a 
large change like this. I got a few comments last time that have been fixed in 
this new version.

This new webrev is based on jdk9/hs-gc and once approved it will be backported 
to jdk8 (to minimize the diff between jdk8 and jdk9).

Let me know if you have some change out that you want to push before I push this 
change. The risk of merge conflicts is high since the change touches a lot of code.

Bug: https://bugs.openjdk.java.net/browse/JDK-8025856

Webrev: http://cr.openjdk.java.net/~jwilhelm/8025856/webrev.1/

Thanks,
/Jesper