Fix(&put): Missing spec in cec

[wjrforcyber]

A tiny fix.
We are missing the spec name after &put, which leads to

./abc -c "read_aiger i10.aig; strash; &get; &put; cec -n"
======== ABC command line "read_aiger i10.aig; strash; &get; &put; cec -n"
The external spec is not given.

After the fix:

./abc -c "read_aiger i10.aig; strash; &get; &put; cec -n"
======== ABC command line "read_aiger i10.aig; strash; &get; &put; cec -n"
Networks are equivalent after structural hashing.  Time =     0.00 sec