I had a look at httpd, and it appears that it doesn't actually use any functions defined in sys/hash.h. Same for md5.h and sha1.h in httpd.c. After removing those includes, it compiles and runs, but I didn't do any serious testing.
Index: usr.sbin/httpd/httpd.c =================================================================== RCS file: /cvs/src/usr.sbin/httpd/httpd.c,v retrieving revision 1.26 diff -u -p -r1.26 httpd.c --- usr.sbin/httpd/httpd.c 22 Nov 2014 00:24:22 -0000 1.26 +++ usr.sbin/httpd/httpd.c 4 Dec 2014 01:04:29 -0000 @@ -22,7 +22,6 @@ #include <sys/stat.h> #include <sys/wait.h> #include <sys/resource.h> -#include <sys/hash.h> #include <net/if.h> #include <netinet/in.h> @@ -40,8 +39,6 @@ #include <unistd.h> #include <ctype.h> #include <pwd.h> -#include <sha1.h> -#include <md5.h> #include "httpd.h" Index: usr.sbin/httpd/parse.y =================================================================== RCS file: /cvs/src/usr.sbin/httpd/parse.y,v retrieving revision 1.42 diff -u -p -r1.42 parse.y --- usr.sbin/httpd/parse.y 20 Nov 2014 05:51:20 -0000 1.42 +++ usr.sbin/httpd/parse.y 4 Dec 2014 01:04:29 -0000 @@ -30,7 +30,6 @@ #include <sys/stat.h> #include <sys/queue.h> #include <sys/ioctl.h> -#include <sys/hash.h> #include <net/if.h> #include <net/pfvar.h> Index: usr.sbin/httpd/server.c =================================================================== RCS file: /cvs/src/usr.sbin/httpd/server.c,v retrieving revision 1.46 diff -u -p -r1.46 server.c --- usr.sbin/httpd/server.c 31 Oct 2014 13:49:52 -0000 1.46 +++ usr.sbin/httpd/server.c 4 Dec 2014 01:04:29 -0000 @@ -24,7 +24,6 @@ #include <sys/un.h> #include <sys/uio.h> #include <sys/tree.h> -#include <sys/hash.h> #include <net/if.h> #include <netinet/in.h> Index: usr.sbin/httpd/server_fcgi.c =================================================================== RCS file: /cvs/src/usr.sbin/httpd/server_fcgi.c,v retrieving revision 1.40 diff -u -p -r1.40 server_fcgi.c --- usr.sbin/httpd/server_fcgi.c 25 Oct 2014 03:23:49 -0000 1.40 +++ usr.sbin/httpd/server_fcgi.c 4 Dec 2014 01:04:29 -0000 @@ -23,7 +23,6 @@ #include <sys/socket.h> #include <sys/un.h> #include <sys/tree.h> -#include <sys/hash.h> #include <net/if.h> #include <netinet/in.h> Index: usr.sbin/httpd/server_file.c =================================================================== RCS file: /cvs/src/usr.sbin/httpd/server_file.c,v retrieving revision 1.39 diff -u -p -r1.39 server_file.c --- usr.sbin/httpd/server_file.c 25 Oct 2014 03:23:49 -0000 1.39 +++ usr.sbin/httpd/server_file.c 4 Dec 2014 01:04:29 -0000 @@ -23,7 +23,6 @@ #include <sys/socket.h> #include <sys/un.h> #include <sys/tree.h> -#include <sys/hash.h> #include <net/if.h> #include <netinet/in.h> Index: usr.sbin/httpd/server_http.c =================================================================== RCS file: /cvs/src/usr.sbin/httpd/server_http.c,v retrieving revision 1.54 diff -u -p -r1.54 server_http.c --- usr.sbin/httpd/server_http.c 25 Oct 2014 03:23:49 -0000 1.54 +++ usr.sbin/httpd/server_http.c 4 Dec 2014 01:04:29 -0000 @@ -23,7 +23,6 @@ #include <sys/socket.h> #include <sys/un.h> #include <sys/tree.h> -#include <sys/hash.h> #include <net/if.h> #include <netinet/in.h>
