Get a parameter value from a shader object

Property definitions

glesv2 :: glesv2 $ Sys :: glGetShaderiv
# Get a parameter value from a `shader` object
fun glGetShaderiv(shader: GLShader, pname: GLGetParameterName): Int `{
	int val;
	glGetShaderiv(shader, pname, &val);
	return val;
`}
lib/glesv2/glesv2.nit:254,1--259,2