RFR: JDK-8254189: Improve comments for StackOverFlow and fix in_xxx() functions [v2]

[Thomas Stuefe]

> Hi,
> 
> may I please have reviews for this small cleanup / fix?
> 
> While reviewing JDK-8253717 it was found that comments would help with understanding the StackOverFlow class. Especially the fact that the various _base_ are actually pointing outside their respective zone, since the stack grows downward and a zone (and the stack itself) range is [end, base). If you don't look at this code daily it can be surprising.
> 
> This also fixes some small off-by-one errors in various "in_stack_xxx_zone()" methods which test whether a given address is inside a zone and gave wrong results for address=base since base points outside its zone. This had the effect that an address could be in multiple zones.
> 
> Finally it adds a small gtest which tests the StackOverFlow methods.

Thomas Stuefe has updated the pull request incrementally with one additional commit since the last revision:

  Feedback David

-------------

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/795/files
  - new: https://git.openjdk.java.net/jdk/pull/795/files/8c128823..cc54ef8d

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=795&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=795&range=00-01

  Stats: 5 lines in 1 file changed: 0 ins; 5 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/795.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/795/head:pull/795

PR: https://git.openjdk.java.net/jdk/pull/795