RFR: 8271003: hs_err improvement: handle CLASSPATH env setting longer than O_BUFLEN [v3]

[Calvin Cheung]

> Please review this small enhancement for addressing the problem of the CLASSPATH env variable setting being truncated in a hs err log.
> 
> For printing a char string, it doesn't need to go through `do_vsnprintf()` which does the truncation based on the input buffer length. The change is local to the code path pertaining to hs err log.
> 
> Testing:
> 
> - [x] tiers 1, 2 (including the new test)

Calvin Cheung has updated the pull request incrementally with one additional commit since the last revision:

  add comment in os.cpp

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/4947/files
  - new: https://git.openjdk.java.net/jdk/pull/4947/files/35eccdc6..9648478c

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=4947&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=4947&range=01-02

  Stats: 1 line in 1 file changed: 1 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4947.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4947/head:pull/4947

PR: https://git.openjdk.java.net/jdk/pull/4947