Lua functionality change: print renamed to mg.write, read renamed to mg.read. Expanded user manual, fixed example pages.

	modified:   mongoose.c

In few windows machines, the environment variables "ProgramFiles" is required to successfully execute PHP code especially socket functions.

when having connections with and without auth would cause double free and then crash

- Added mg.onerror, mg.include, mg.redirect
- mg.onerror, if overridden, lets the user trap syntax errors and
  other loadbuffer errors, and dump stack traces and debug info
  for uncaught runtime errors.
- Log unexpected errors from mg.onerror handlers
- Provide mg.cry so custom handlers can reproduce default behavior
- Call mg.onerror handler before unwinding stack
- If mg.onerror returns non-0, stop loading chunks
- Included pages stop parent page processing if mg.onerror returns non-zero
- Included pages don't sent HTTP errors, they throw lua errors

1. fix a bug that when header contains "Range: 100-", the range request
support will fail
2. (windows) fix a bug that when explorer.exe crashes due to some
reason, the tray icon will disappear.