Add meta-variables that are useful for outputting logs

[zero-plusplus]

Add two meta-variables that are useful for outputting logs.

• {now} - Same as {A_Year}-{A_Mon}-{A_MDay} {A_Hour}:{A_Min}:{A_Sec}.{A_MSec}
• {callstack} - An array of objects with call stack details
  • {callstack[n].name} - It is similar to A_ThisFunc, but returns the same string as the notation displayed in the call stack view. Unlike it, it does not return an empty string during the AutoExec section. Therefore, it is a little more informative than that
  • {callstack[n].path} - Full path of the file
  • {callstack[n].line} - Line of the file
• {thisCallstack} - Short hand of {callstack[1].name}