This new print clarifies what the next set of prints are referring to.

It also slightly optimises the subsequent control flow.

This allows user to specify their own PAPI events (up to MAXNPAPICNTRS, defaulting to 4).
This is done with the DR_HOOK_PAPI_COUNTERS flag. If the flag is not specified, and PAPI
is enabled, then the following defaults will be chosen:
PAPI_TOT_CYC
PAPI_FP_OPS
PAPI_L1_DCA
PAPI_L2_DCM

If an invalid event is chosen, then DrHook will simply crash will an appropriate error message.

This commit removes all tabs, in favour of two spaces, in files touched by ecmwf-ifs#26 and ecmwf-ifs#27.