Fix enum string generation

Should be "ENUM_NAME" "enum_nick" not "enum_nick" "enum_nick".
Clean up get_bounding_box for composer/composer3

It is safe to write to one of the inputs of gegl_rectangle_bounding_box
so the deep if chain is unnecessary.
Make box-blur.cl match the committed box-blur.cl.h
Clean up formatting in box-blur.cl
warp.c: make sure the stamp influence LUT is big enough
operations/warp: Fix errors with gauss function and floating point rounding.
common/warp: make sure the stamp lut is always big enough
common/warp: fix interpolation reversal
common/warp: do not factor stamp size into the the influence - bigger brushes will do nothing
common/warp: free stamp lut when done with processing
operations: Port apply-lens filter from GIMP
tests: Add test cases for apply-lens
common/warp: free stamp lut only when its allocated first
operations: remove minor redundant assignment
operations: Make linear sRGB using sRGB D65 white point
opencl: Do not ignore the CL error
buffer: minor clean up
operations: minor clean-up
Add support for filtering non-LGPL plugins

Add support for filtering operations with more restrictive
licenses (e.g. GPL) at runtime, by default only operations
with licenses no more restrictive than LGPL are exposed.
tests: Add test case for license filter