RFR: 8255741: Zero: print signal name in unhandled signal handler [v2]

[Aleksey Shipilev]

> At least one test -- `runtime/Safepoint/TestAbortVMOnSafepointTimeout.java` -- fails on Zero with:
> 
> # Internal Error (/home/shade/trunks/jdk/src/hotspot/os_cpu/linux_zero/os_linux_zero.cpp:250), pid=560280, tid=560281
> # fatal error: caught unhandled signal 4
> 
> The test expects "SIGKILL (sent by kill)" in the test output.
> 
> Additional testing:
>  - [x] `TestAbortVMOnSafepointTimeout.java` now passes on Linux x86_64 Zero.

Aleksey Shipilev has updated the pull request incrementally with one additional commit since the last revision:

  Minor stylistic change

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/1001/files
  - new: https://git.openjdk.java.net/jdk/pull/1001/files/89de8c27..3356bd3f

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=1001&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=1001&range=00-01

  Stats: 3 lines in 1 file changed: 1 ins; 1 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1001.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1001/head:pull/1001

PR: https://git.openjdk.java.net/jdk/pull/1001