r7.1

• Add Meson build system.

r7

• Squeeze a bit of speed by replacing some multiplication and division with bit shift.

r6

• Fix crash that a frame reference is not properly freed.

r5

Add 9-16 bits support

r4

Use C++ casting operator instead of C-style type casting.
Code cleanup.

r3

Avoid possibly non-threadsafe behavior

r2

Fix error that mthresh and vthresh was not properly initialized

and allocate buffer in getframe to prevent from being written by more
than one thread

r1

Cosmetics