nsl inout flow qualifier

[aconstlink]

For nsl, an inout flow specifier would be nice if input and output types match. This would further reduce code bloat.

in vec3_t pos : position ;
in vec3_t nrm : normal ;
out vec4_t pos : position ;
out vec3_t nrm : normal ;

Could be

in vec3_t pos : position ;
out vec4_t pos : position ;
inout vec3_t nrm : normal ;

Or if possible to input a vec4 position:

inout vec4_t pos : position ;
inout vec3_t nrm : normal ;
inout vec2_t tx : texcoord ;