Make GnuPG more PIE-friendly

[Diego Elio Pettenò]

Hi,

since I have been looking at the GnuPG sources for the card issues I got, I
took a bit of time to pass the object files through my cowstats[1] script
(on a PIE[2],[3] build).

The result is in these three patches that move some data structures to
.rodata to avoid relocations due to pointers, reduce resident memory size,
and add extra safety (as overflows can't risk changing seed data for
instance).

HTH,
-- 
Diego Elio Pettenò