Fix PR lib/39185
Partly restore the changes which were removed during the Heimdal 1.1 update:
src/lib/libasn1/Makefile 1.28 -> 1.29
src/lib/libhdb/Makefile 1.21 -> 1.22
src/crypto/dist/heimdal/lib/asn1/gen.c 1.8 -> 1.9
Add .hx support in 'new' heimdal libraries:
src/lib/libgssapi/Makefile
src/lib/libhx509/Makefile
Add a new entry in doc/HACKS for this changes.