ESP are the only partitions we're detecting through their pt_type
(modulo 0x12 which was Compaq Diagnostic & unlikely to be found on
GPT...)

However GPT has no equivalent to pt_type
But we can test for ESP flag

done separatly in order to have a better history for simplify then
introducing new API

create directly the hash in XS instead of instead of sprintf()ing it
into a string which was then parsed in perl in order to actually create
the hash

this fixes several issues:
- due to adding some fields to the string under if (),
  we could silently have ignored some partitions
-

this also simplifies adding further fields