* src/w32-add.h: Remove hack to define pid_t.
* src/gpg-error.h.in: Eval macro to define pid_t.
* src/mkheader.c (have_sys_types_h, sys_types_h_included): New.
(parse_config_h): Test for sys/types.h.
(write_special): Protect inclusion of sys/types.h.  Define new macro
'define:pid_t'.