Adjusted URLs

Most of these sites support HTTPS (some forward to HTTPS when accessing
the HTTP versions). Use HTTPS directly if supported.

Some URLs led to 404 error pages. Adjusted the links to point to
new locations.

I did not adjust the Microsoft HTML Help Workshop link because it seems
that this software is not available anymore. Instead of removing the
link entirely I kept it there in case it helps someone to find the
software on archived websites.

linkhash.c

@@ -65,7 +65,7 @@ int lh_ptr_equal(const void *k1, const void *k2)
 
 /*
  * hashlittle from lookup3.c, by Bob Jenkins, May 2006, Public Domain.
- * http://burtleburtle.net/bob/c/lookup3.c
+ * https://burtleburtle.net/bob/c/lookup3.c
  * minor modifications to make functions static so no symbols are exported
  * minor modifications to compile with -Werror
  */
@@ -156,7 +156,7 @@ satisfy this are
    14  9  3  7 17  3
 Well, "9 15 3 18 27 15" didn't quite get 32 bits diffing
 for "differ" defined as + with a one-bit base and a two-bit delta.  I
-used http://burtleburtle.net/bob/hash/avalanche.html to choose
+used https://burtleburtle.net/bob/hash/avalanche.html to choose
 the operations, constants, and arrangements of the variables.
 
 This does not achieve avalanche.  There are input bits of (a,b,c)
@@ -287,7 +287,7 @@ static uint32_t hashlittle(const void *key, size_t length, uint32_t initval)
 		 * still catch it and complain.  The masking trick does make the hash
 		 * noticeably faster for short strings (like English words).
 		 * AddressSanitizer is similarly picky about overrunning
-		 * the buffer. (http://clang.llvm.org/docs/AddressSanitizer.html
+		 * the buffer. (https://clang.llvm.org/docs/AddressSanitizer.html)
 		 */
 #ifdef VALGRIND
 #define PRECISE_MEMORY_ACCESS 1