[11u] RFR: 8173361: various crashes in JvmtiExport::post_compiled_method_load

[Lindenmaier, Goetz]

Hi, 

I downport this for parity with 11.0.10-oracle.
The code does not fit very well.
I removed a guarantee because is_unloading() does not exist in 11.
I turned some MutexLocker to MutexLockerEx which takes the 
Mutex::_no_safepoint_check_flag enum argument.

http://cr.openjdk.java.net/~goetz/wr20/8173361-post_compiled_method-jdk11/01/webrev/

Please review.

There are some follow up changes for jvmti which all need similar adaptions.

https://bugs.openjdk.java.net/browse/JDK-8173361
https://hg.openjdk.java.net/jdk/jdk/rev/e79ece2eb1ba

Best regards,
  Goetz