Callbacks created by NewCallbackCDecl were never released and then
they are leaked, especially when the window size was changed by
SetWindowSize on Windows.
This change defines new callback ID types with uintptr, and reuse
the callbacks.
Closes#1672
This change adds APIs to enable to use system cursor shapes other
than the default shape (an arrow).
This change doesn't add these cursors since they seem a little
different on macOS from the other platforms.
* GLFW_HRESIZE_CURSOR
* GLFW_VRESIZE_CURSOR
Closes#995
Go's int can be 64bit or 32bit, while C's int is always 32bit on
Windows in Ebiten usage. For C's int argument, do not pass Go's
int pointer or broken values are set.
Related to #829
