Add tmp dir in files ignored by git
"Hello, world!" modified to use proper calling convention, including save & restore registers
Add "Hello, world!" example in C - will be used for C compiler demonstration
Several CPU and logging updates

- new instructions added: CMP, JS, JNS
- flag 's' added
- fixed several instructions to comply with "what, where" pattern of
  operands
- fixed initial SP setting
- debug logging improved