use enough memory for pin verification/modification structure
Use C99 flexible array member

The structures PIN_MODIFY_STRUCTURE and PIN_VERIFY_STRUCTURE now use a
C99 flexible array member when available for abData field.

uint8_t abData[];

See http://lists.alioth.debian.org/pipermail/pcsclite-cvs-commit/2013-May/006191.html
enable compiler warnings by default