setup options to link custom libraries to scallion

use '--tor-lib lib' for each custom library you'd like to link to scallion.
tor will be built by passing '-llib' to the linker.

for example:
./setup build --tor-prefix /home/user/customtor -i /home/user/customlib -l /home/user/customlib --tor-lib customlib

this will link 'customlib' to scallion, looking in /home/user/customlib
for header files and /home/user/customlib for the lib.