add "experimental!" warning to linetrace directive
add "experimental!" warning to linetrace directive

c-blake/cython,ChristopherHogan/cython,hhsprings/cython,marscher/cython,hhsprings/cython,andreasvc/cython,roxyboy/cython,encukou/cython,mrGeen/cython,slonik-az/cython,fperez/cython,andreasvc/cython,fabianrost84/cython,mrGeen/cython,marscher/cython,madjar/cython,dahebolangkuan/cython,andreasvc/cython,achernet/cython,madjar/cython,ABcDexter/cython,JelleZijlstra/cython,fperez/cython,slonik-az/cython,da-woods/cython,cython/cython,madjar/cython,acrispin/cython,dahebolangkuan/cython,ChristopherHogan/cython,mcanthony/cython,ABcDexter/cython,acrispin/cython,hickford/cython,mrGeen/cython,cython/cython,hickford/cython,hickford/cython,scoder/cython,encukou/cython,hickford/cython,scoder/cython,slonik-az/cython,fperez/cython,slonik-az/cython,fabianrost84/cython,encukou/cython,ChristopherHogan/cython,madjar/cython,roxyboy/cython,encukou/cython,c-blake/cython,hhsprings/cython,cython/cython,roxyboy/cython,mcanthony/cython,roxyboy/cython,fabianrost84/cython,hhsprings/cython,da-woods/cython,mcanthony/cython,acrispin/cython,mrGeen/cython,roxyboy/cython,fabianrost84/cython,JelleZijlstra/cython,cython/cython,c-blake/cython,dahebolangkuan/cython,hickford/cython,achernet/cython,mcanthony/cython,acrispin/cython,dahebolangkuan/cython,madjar/cython,JelleZijlstra/cython,dahebolangkuan/cython,marscher/cython,andreasvc/cython,achernet/cython,ABcDexter/cython,da-woods/cython,JelleZijlstra/cython,fperez/cython,scoder/cython,c-blake/cython,fabianrost84/cython,encukou/cython,mcanthony/cython,c-blake/cython,marscher/cython,mrGeen/cython,andreasvc/cython,slonik-az/cython,scoder/cython,da-woods/cython,acrispin/cython,achernet/cython,fperez/cython,hhsprings/cython,ABcDexter/cython,achernet/cython,ABcDexter/cython,marscher/cython,JelleZijlstra/cython