RFR(S): 8247516: DSO.closestSymbolToPC() should use dbg.lookup() rather than rely on java ELF file support

[Chris Plummer]

Hello,

Please review the following:
https://bugs.openjdk.java.net/browse/JDK-8247516
http://cr.openjdk.java.net/~cjplummer/8247516/webrev.00/index.html

I put all the details in the description of the CR, including some 
background on how symbol lookups are done, including what LoadObjects 
are and their class hierarchy, and also info on JVMDebugger subclasses.

One thing not covered in the bug description is the additional gutting 
of DSO.java that comes with these changes. Many APIs were not used so I 
removed them, such as setBase(), lookupSymbol(), and isDSO(). Doing so 
allowed completely severing any need for java ELF file support. Note I 
plan on removing the java ELF file support itself with another CR after 
pushing these changes.

thanks,

Chris