Commit Briefs
fix various compilation errors
Include gmid.h as first header in every file, as it then includes config.h (that defines _GNU_SOURCE for instance). Fix also a warning about unsigned vs signed const char pointers in openssl.
don't allocate BIGNUM on the stack
on fedora 33 the BIGNUM type is opaque. Allocate always to avoid headaches.
revert commit 346f28eeaa205d268d1e63c7ffd86cf041f6d1e6
keep mark_nonblock in utils.c, as otherwise the build for the regress suite will fail (mark_nonblock needs fatal which is in gmid.c, and we can't link gmid.o with the regress suite...)