vips.h: problem with vips_init()
vips.h: problem with vips_init()

For version prior 7.41, vips_init() is a macro to VIPS_INIT().
VIPS_INIT() should be called, but as it is a macro, cgo could not
determine the return type, hence making the build fail.
So, we undef vips_init(), and define the vips_init() method.

Dal-Papa/bimg,greut/bimg,greut/bimg,h2non/bimg,denji/bimg,h2non/bimg,greut/bimg,Dal-Papa/bimg,denji/bimg,h2non/bimg