Pressing Ctrl-C while a program loads make the program hang

[fachat]

After implementing #29 , when pressing Ctrl-C (RUN/STOP) while the loader is loading the file to be executed, terminates the loader, but does not free the SENDBUF PSEM.
This makes the system hang on each function that uses SENDBUF

[fachat]

This should automatically be fixed when implementing the new buffer / streams handling in NG - so won't fix here.

[fachat]

Addition: similar problems appear when the child process is suspended (e.g. via Ctrl-Z) while still in the loading process.

[fachat]

Implementation idea for NG buffer/send/receive:

• alloc a new buffer for stream
• put everything to be sent into buffer
• send buffer non-blocking
• register stream and buffer with the child task registry
• wait for reply from child, but check signals at that same time
• if signal received, return
• handle any checks in further waitpid/checksig calls

Note: need to check for race conditions.