x86_64 compiler script is done
Unclosed '[' at the end will be reported for the compiler.

Modified error handling mechanism of compiler core so that unclosed
'[' will be reported correctly.
Fixed error handler and EOF handler.

Added error handler while feeding codes and completing pseudocode generation.
Besides, added EOF handler so that the program can terminate correctly.
Corrected EOF detector. Double Ctrl-D is not needed when operating
bfc in terminal.