Restore "Add new hashing and "hash with state" infrastructure"

This reverts commit e6a172f,
which was a revert of a3bf60f.

Add new hashing and "hash with state" infrastructure

This adds support for three new hash functions: StadtX, Zaphod32 and SBOX,
and reworks some of our hash internals infrastructure to do so.

SBOX is special in that it is designed to be used in conjuction with any
other hash function for hashing short strings very efficiently and very
securely. It features compile time options on how much memory and startup
time are traded off to control the length of keys that SBOX hashes.

This also adds support for caching the hash values of single byte characters
which can be used in conjuction with any other hash, including SBOX, although
SBOX itself is as fast as the lookup cache, so typically you wouldnt use both
at the same time.

This also *removes* support for Jenkins One-At-A-Time. It has served us
well, but it's day is done.

This patch adds three new files: zaphod32_hash.h, stadtx_hash.h,
sbox32_hash.h

MANIFEST

@@ -5200,8 +5200,10 @@ regexp.h			Public declarations for the above
 regnodes.h			Description of nodes of RE engine
 run.c				The interpreter loop
 runtests.SH			A script that generates runtests
+sbox32_hash.h			SBox hash code (32 Bit SBOX based hash function)
 scope.c				Scope entry and exit code
 scope.h				Scope entry and exit header
+stadtx_hash.h			StadtX hash code (64 Bit fast hash function)
 sv.c				Scalar value code
 sv.h				Scalar value header
 symbian/bld.inf			Symbian sample app build config
@@ -6020,3 +6022,4 @@ win32/wince.h			WinCE port
 win32/wincesck.c		WinCE port
 write_buildcustomize.pl		Generate lib/buildcustomize.pl
 XSUB.h				Include file for extension subroutines
+zaphod32_hash.h			Zaphod32 hash code (32 bit fast hash function)

embedvar.h

@@ -384,10 +384,14 @@
 #define PL_Gdollarzero_mutex	(my_vars->Gdollarzero_mutex)
 #define PL_fold_locale		(my_vars->Gfold_locale)
 #define PL_Gfold_locale		(my_vars->Gfold_locale)
+#define PL_hash_chars		(my_vars->Ghash_chars)
+#define PL_Ghash_chars		(my_vars->Ghash_chars)
 #define PL_hash_seed		(my_vars->Ghash_seed)
 #define PL_Ghash_seed		(my_vars->Ghash_seed)
 #define PL_hash_seed_set	(my_vars->Ghash_seed_set)
 #define PL_Ghash_seed_set	(my_vars->Ghash_seed_set)
+#define PL_hash_state		(my_vars->Ghash_state)
+#define PL_Ghash_state		(my_vars->Ghash_state)
 #define PL_hints_mutex		(my_vars->Ghints_mutex)
 #define PL_Ghints_mutex		(my_vars->Ghints_mutex)
 #define PL_keyword_plugin	(my_vars->Gkeyword_plugin)