PAPI examples: Update src/examples to remove compilation warnings and properly run

[Treece-Burgess]

Pull Request Description

A user would encounter the following if running make under src/examples:

PAPI_state.c:46:4: warning: implicit declaration of function ‘printstate’; did you mean ‘initstate’? [-Wimplicit-function-declaration]
   46 |    printstate(status);
      |    ^~~~~~~~~~
      |    initstate
PAPI_set_domain.c: In function ‘main’:
PAPI_set_domain.c:78:4: warning: implicit declaration of function ‘close’; did you mean ‘pclose’? [-Wimplicit-function-declaration]
   78 |    close(fd);
      |    ^~~~~
      |    pclose
locks_pthreads.c:39:4: warning: implicit declaration of function ‘usleep’ [-Wimplicit-function-declaration]
   39 |    usleep(SLEEP_VALUE);
      |    ^~~~~~

Furthermore, a user would encounter errors/incorrect behavior with the following tests:

1. PAPI_get_opt.c - the EventSet was not bound to a component before calling PAPI_set_opt( ... )
2. multiplex.c - the EventSet was not bound to a component before calling PAPI_set_multiplex( ... )
3. PAPI_reset.c - did not properly show an EventSet's counter values being reset as the perf_event component resets counter values upon the call to PAPI_start

All of the above is resolved in this PR.

Testing

Testing was done on Godzilla at Oregon (Intel Xeon Gold E5-2680 v4) and from testing the aforementioned compilation warnings are resolved and the updated examples run successfully.

Author Checklist

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• Tests
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