Enhance stability of tests and prepare for inclusion of appveyor

[matthiasblaesing]

Running the JNA unittests on the appveyor CI system shows, that implicit assumptions
in the unittests don't hold everywhere. There are:

• corner cases in the behavior of Win32 functions
• missing dependencies (several of the COM tests depend on one of the office products)
• wrong invocations (the Win32DemoService picks up a system wide installed old JNA dll)
• disabled service
  and so on.

The referenced commits either express the assumptions as junit assumption (causing the
affected tests to be skipped) or fix/improve the behavior.

Closes: #685

[matthiasblaesing]

@dblock could you please have a look at this setup? I think I got everything tackled - my builds on appveyor run mostly clean, unittests on my development setup still run
@dbwiddis could you please also have a look? I modified the Pdh bindings: 14b746f as the Util method errored out on appveyor. I think the new version is more close to the original spirit of the base method and also matches what you initially implemented (using a result object, instead of a list of lists).

[dbwiddis]

Looks good, although in my application, I remove the "_Total" instance from the list, so it doesn't work with the unmodifiable lists you've used so I'm having to change my iteration. I'm curious the reason to include that?

[dblock]

Looks great, I would add some CHANGELOG and consider @dbwiddis' comment above. Good to merge AFAIK @matthiasblaesing. Great work.

[dbwiddis]

Another small issue. When attempting to use PdhEnumObjectItems with an invalid search string, I receive the error -1073738824 = 0xc0000bb8 (The specified object was not found on the system.) However, in the process throwing the Win32Exception with that value, it loses the value and ends up throwing a LastErrorException:

Exception in thread "main" com.sun.jna.LastErrorException: GetLastError() returned 317
at com.sun.jna.platform.win32.Kernel32Util.formatMessage(Kernel32Util.java:196)
at com.sun.jna.platform.win32.Kernel32Util.formatMessage(Kernel32Util.java:216)
at com.sun.jna.platform.win32.Win32Exception.(Win32Exception.java:69)
at com.sun.jna.platform.win32.Win32Exception.(Win32Exception.java:56)

The constructor for Win32Exception with an int implies it expects values in the range -32K to 32K (the lasterror values). I believe the error value may need a different / its own exception type. Happy to code that up in another PR if you would like.

[matthiasblaesing]

@dbwiddis I agree, that the Win32Exception does not work for this usecase. I introduced a PdhException, that basicly just reports the error code. I also added a matching unittest.

For the modifiable lists: I have mixed feelings here. I like immutable objects, but I see your use case.

Please have another look:
2898fba

[dbwiddis]

Looks good here.

[matthiasblaesing]

@dblock @dbwiddis thank you both for having a look!