Make srr -e work on RAR files too

[Gfy]

heh, "srr -e" can display the list of blocks in a .rar, 
but the .rar extension needs to be changed to .srr first
eg, srr -e file.rar.srr
"srr -e file.rar" creates a .srr 
Gfy, maybe that should change? (so "srr -e file.rar" shows the blocks)
srr knows the difference. for a (real) .rar, 
-e shows "The file is a RAR file." before listing the blocks. 
for a (real) .srr, -e shows "The file is an SRR file."