Enable ctrl-c during ctrl-c handling and improve error logging

Commit a235f79f adds an ability to print useful information on ctrl-c. However, with-handlers itself disables further ctrl-c. This could be problematic when ctrl-c handling takes long time and users want to terminate the program right away. Therefore, we switch to use with-handlers* instead, which allows ctrl-c inside ctrl-c handling.

Also, switch from string port to pipe port. This allows us to use in-lines to gradually process information, rather than computing on a very large string at once (which could appear to be hanging for several minutes).