fixes issue 1055 + initialize set_libc to NULL
fixes issue 1055
+ initialize set_libc to NULL

SVN-Revision: 1069

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