Clipboard, RemoteApp, Cursor + Color Conversion

Clipboard:
* xfreerdp: migrate xf_cliprdr.c to callback interface
* wfreerdp migrate wf_cliprdr.c to callback interface
* channels/clipboard: add missing callbacks and definitions
* libwinpr-clipboard: add reusable clipboard format synthesizer

RemoteApp:
* wfreerdp: stub RemoteApp callback interface, add WIP implementation

Cursor + Color Conversion:
* Add new cursor conversion function, fix issue #1772
* Add new function for monochrome bitmap conversion
* Purge HCLRCONV dependency from libfreerdp-gdi, xfreerdp