Replace all random functions with isc_random, isc_random_buf and isc_random_uniform API.

The three functions has been modeled after the arc4random family of
functions, and they will always return random bytes.

The isc_random family of functions internally use these CSPRNG (if available):

1. getrandom() libc call (might be available on Linux and Solaris)
2. SYS_getrandom syscall (might be available on Linux, detected at runtime)
3. arc4random(), arc4random_buf() and arc4random_uniform() (available on BSDs and Mac OS X)
4. crypto library function:
4a. RAND_bytes in case OpenSSL
4b. pkcs_C_GenerateRandom() in case PKCS#11 library

contrib/sdb/sqlite/zone2sqlite.c

@@ -16,7 +16,6 @@
 
 #include <dns/db.h>
 #include <dns/dbiterator.h>
-#include <isc/entropy.h>
 #include <dns/fixedname.h>
 #include <isc/hash.h>
 #include <dns/name.h>
@@ -148,7 +147,6 @@ main(int argc, char *argv[])
     dns_rdataset_t rdataset;
     dns_rdata_t rdata = DNS_RDATA_INIT;
     isc_mem_t *mctx = NULL;
-    isc_entropy_t *ectx = NULL;
     isc_buffer_t b;
     isc_result_t result;
 
@@ -167,8 +165,6 @@ main(int argc, char *argv[])
     
     result = isc_mem_create(0, 0, &mctx);
     check_result(result, "isc_mem_create");
-    result = isc_entropy_create(mctx, &ectx);
-    check_result(result, "isc_entropy_create");
     
     isc_buffer_init(&b, porigin, strlen(porigin));
     isc_buffer_add(&b, strlen(porigin));
@@ -284,7 +280,6 @@ main(int argc, char *argv[])
     
     dns_dbiterator_destroy(&dbiter);
     dns_db_detach(&db);
-    isc_entropy_detach(&ectx);
     isc_mem_destroy(&mctx);
 
     closeandexit(0);