memcpy transform to sw with unaligned buffers

test_aligment.zip

     2: 00000020     1 OBJECT  LOCAL  DEFAULT    3 c
     8: 00000021     8 OBJECT  GLOBAL DEFAULT    3 b
     7: 00000030     8 OBJECT  GLOBAL DEFAULT    3 a

80000088 bar:
...
80000098: 00 00 12 00 63 61 00 00       move r2, 0x21
800000a0: 00 00 02 44 08 7c 00 00       sw r2, 0x0, r1

as c makes b not aligned on 8 bytes, the transformation of memcpy to sw is not legal and produces a memory fault at runtime.

Seen initially from tests in supertest:

4/11/2/3/t2.c		
4/11/3/1/t1.c
C99/7/21/2/3/t2.c		
C99/7/21/3/1/t1.c

fix by c8c7ca7623a