Renamed rc4 -> arcfour.

Rev: src/symmetric/Makefile.am.in:1.6
Rev: src/symmetric/arcfour.c:1.1
Rev: src/symmetric/include/arcfour.h:1.1
Rev: src/symmetric/include/rc4.h:1.5(DEAD)
Rev: src/symmetric/rc4.c:1.3(DEAD)