Add API to access the process id of the started process

Added new agent message "GetProcessId" and a API "winpty_get_process_id"
to allow access to the process id of the started process. The process id
is needed to integrate "winpty" with Eclipse CDT to launch native Windows
console applications inside the Eclipse UI.
Simplify patch by using GetProcessId

GetProcessId simplifies the code as it avoids to add the additional member variable 'm_childProcessId'. Cleaned up the indentation.
Fixed indentation

Fixed indentation by replacing TABs by 4 spaces.
Merge pull request #14 from ustieber/patch-1-GetProcessId

Add API to access the process id of the started process
Add support for a non-terminal console mode

If a process is running under control of winpty, the output of the process is decorated with ESC sequences to control a terminal to print the process output nicely. In some environments however, the client showing the output to the user is not a full terminal emulation, the Eclipse CDT debug console view in example, and the ESC sequences are printed as output additional to the real process output. This commit is adding an API function to switch into a mode where winpty is not decorating the process output with ESC sequences. The console mode is designated to pass on the process output to the client as is.
Merge pull request #15 from ustieber/patch-2-ConsoleMode

Add support for a non-terminal console mode