Easygraphics

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* fix: legacy and music subpackage not packed in the binary distributions.

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* fix: delay_fps() now work properly in Manual render mode
* finish chinese translations for tutorials

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* add: load_image() to load image from files
* add: to_alpha() to make a transparently color
* change: use Source Over as the default composition mode (the same with Qt)
* more tutorials
* add: show_table() to display table infomation in a dialog
* change: rename mouse_msg() to has_mouse_msg()
* change: rename kb_hit() to has_kb_hit()
* change: rename get_mouse() to get_mouse_msg()
* change: rename kb_msg() to has_kb_msg()
* finish the tutorials.

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* add: reflection (mirror/flip) and shear (skew) operations.

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* add: headless mode support (no graphics window mode, use it to draw pictures)

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* add: easygraphics.legacy package to better compatible with old BGI programs.
* add: get_click() function to get mouse click event
* change: background implementation to make set_background_color() work correctly
* add: now can use name ("red"), color string ("ff0000), integer color rgb value (0xff0000) \
in set_color(), set_fill_color(), set_background_color() functions
* add: cymk() and hsv() to get CYMK and HSV format color
* more tutorials