Support -hwndparent parameter for mRemoteNG, Remote4Support and others

[meyergru]

Please support the -hwndparent parameter, like desribed here:

https://github.com/garnbleiche/PuTTY_R4S

Otherwise, KiTTY cannot be used correctly as a PuTTY replacement for tools like mRemoteNG and Remote4Support.

See also:

robertpopa22/mRemoteNG#80