use 4-byte stores in replace_memset for better performance
use 4-byte stores in replace_memset for better performance

fixes issue 247

SVN-Revision: 128

sigma-random/drmemory,LohithBlaze/drmemory,LohithBlaze/drmemory,code4bones/drmemory,sigma-random/drmemory,LohithBlaze/drmemory,sigma-random/drmemory,LohithBlaze/drmemory,code4bones/drmemory,LohithBlaze/drmemory,sigma-random/drmemory,code4bones/drmemory,sigma-random/drmemory,code4bones/drmemory,code4bones/drmemory