Enable assembler optimizations on earlier ARM cores

* cipher/blowfish-armv6.S => cipher/blowfish-arm.S: adapt to pre-armv6 CPUs.
* cipher/blowfish.c: enable assembly on armv4/armv5 little-endian CPUs.
* cipher/camellia-armv6.S => cipher/camellia-arm.S: adapt to pre-armv6 CPUs.
* cipher/camellia.c, cipher-camellia-glue.c: enable assembly on armv4/armv5
  little-endian CPUs.
* cipher/cast5-armv6.S => cipher/cast5-arm.S: adapt to pre-armv6 CPUs.
* cipher/cast5.c: enable assembly on armv4/armv5 little-endian CPUs.
* cipher/rijndael-armv6.S => cipher/rijndael-arm.S: adapt to pre-armv6 CPUs.
* cipher/rijndael.c: enable assembly on armv4/armv5 little-endian CPUs.
* cipher/twofish-armv6.S => cipher/twofish-arm.S: adapt to pre-armv6 CPUs.
* cipher/twofish.c: enable assembly on armv4/armv5 little-endian CPUs.

Our ARMv6 assembly optimized code can be easily adapted to earlier CPUs.
The only incompatible place is rev instruction used to do byte swapping.
Replace it on <= ARMv6 with a series of 4 instructions.

Compare:

   ECB/Stream         CBC             CFB             OFB             CTR
--------------- --------------- --------------- --------------- ---------------

AES 620ms 610ms 650ms 680ms 620ms 630ms 660ms 660ms 630ms 630ms
CAMELLIA128 720ms 720ms 780ms 790ms 770ms 760ms 780ms 780ms 770ms 760ms
CAMELLIA256 910ms 910ms 970ms 970ms 960ms 950ms 970ms 970ms 960ms 950ms
CAST5 820ms 820ms 930ms 920ms 890ms 860ms 930ms 920ms 880ms 890ms
BLOWFISH 550ms 560ms 650ms 660ms 630ms 600ms 660ms 650ms 610ms 620ms

   ECB/Stream         CBC             CFB             OFB             CTR
--------------- --------------- --------------- --------------- ---------------

AES 130ms 140ms 180ms 200ms 160ms 170ms 190ms 200ms 170ms 170ms
CAMELLIA128 150ms 160ms 210ms 220ms 200ms 190ms 210ms 220ms 190ms 190ms
CAMELLIA256 180ms 180ms 260ms 240ms 240ms 230ms 250ms 250ms 230ms 230ms
CAST5 170ms 160ms 270ms 120ms 240ms 130ms 260ms 270ms 130ms 120ms
BLOWFISH 160ms 150ms 260ms 110ms 230ms 120ms 250ms 260ms 110ms 120ms

[ jk: in camellia.h and twofish.c, USE_ARMV6_ASM => USE_ARM_ASM ]
[ jk: fix blowfish-arm.S when __ARM_FEATURE_UNALIGNED defined ]
[ jk: in twofish.S remove defined(HAVE_ARM_ARCH_V6) ]
[ jk: ARMv6 => ARM in comments ]

• Signed-off-by: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>