[foreign] RFR - JDK-8223033 panama_foreign.md should have a basic hello world example

[Jim Laskey]

Updated.

webrev: http://cr.openjdk.java.net/~jlaskey/8223003/webrev-02 <http://cr.openjdk.java.net/~jlaskey/8223003/webrev-02>


> On Apr 26, 2019, at 11:53 AM, Sundararajan Athijegannathan <sundararajan.athijegannathan at oracle.com> wrote:
> 
> * #endif clause missing in header file helloworld.h
> 
> * compiler instructions to built shared object is missing (in other example, shared object exists already)
> Something like:
> 
> cc -shared -o helloworld.dylib helloworld.c
> 
> * File names may be specified for helloworld.h, helloworld.c (perhaps by comment)
> 
> -Sundar
> 
> On 26/04/19, 8:09 PM, Jim Laskey wrote:
>> webrev: http://cr.openjdk.java.net/~jlaskey/8223003/webrev-01
>> jbs: https://bugs.openjdk.java.net/browse/JDK-8223033
>>