-2 can't be converted to GLenum
Getting this error with nim devel, works after commenting out lines 361 - 365 in opengl.nim, trying to make GLenum(uint32) from negative value.
```
GL_NEXT_BUFFER_NV*: GLenum = GLenum(-2)
GL_SKIP_COMPONENTS4_NV*: GLenum = GLenum(-3)
GL_SKIP_COMPONENTS3_NV*: GLenum = GLenum(-4)
GL_SKIP_COMPONENTS2_NV*: GLenum = GLenum(-5)
GL_SKIP_COMPONENTS1_NV*: GLenum = GLenum(-6)
```