Make OS::delay_usec() more reliable on UNIX
Make OS::delay_usec() more reliable on UNIX

Implemented with `nanosleep()`. `usleep()` is deprecated.
Also loops to ensure that __at least__ the requested time is waited, accounting for spurious interruptions.

May help in situations like reattempting to connect to the debugger.

n-pigeon/godot,BastiaanOlij/godot,mcanders/godot,BastiaanOlij/godot,Shockblast/godot,Paulloz/godot,jejung/godot,Brickcaster/godot,ex/godot,guilhermefelipecgs/godot,NateWardawg/godot,Brickcaster/godot,Brickcaster/godot,akien-mga/godot,FateAce/godot,ex/godot,ZuBsPaCe/godot,firefly2442/godot,okamstudio/godot,Paulloz/godot,vnen/godot,sanikoyes/godot,vkbsb/godot,Faless/godot,RandomShaper/godot,Shockblast/godot,Faless/godot,NateWardawg/godot,guilhermefelipecgs/godot,zicklag/godot,Valentactive/godot,josempans/godot,FateAce/godot,jejung/godot,godotengine/godot,ageazrael/godot,MarianoGnu/godot,sanikoyes/godot,RandomShaper/godot,Valentactive/godot,Faless/godot,RandomShaper/godot,ZuBsPaCe/godot,Shockblast/godot,honix/godot,FateAce/godot,Paulloz/godot,ZuBsPaCe/godot,Zylann/godot,guilhermefelipecgs/godot,BastiaanOlij/godot,jejung/godot,godotengine/godot,Brickcaster/godot,vnen/godot,josempans/godot,vnen/godot,pkowal1982/godot,akien-mga/godot,jejung/godot,guilhermefelipecgs/godot,josempans/godot,pkowal1982/godot,vkbsb/godot,Zylann/godot,josempans/godot,Shockblast/godot,vkbsb/godot,vkbsb/godot,vkbsb/godot,akien-mga/godot,Paulloz/godot,ex/godot,sanikoyes/godot,honix/godot,BastiaanOlij/godot,okamstudio/godot,vnen/godot,akien-mga/godot,Shockblast/godot,ageazrael/godot,godotengine/godot,sanikoyes/godot,ex/godot,firefly2442/godot,godotengine/godot,pkowal1982/godot,Faless/godot,okamstudio/godot,Brickcaster/godot,sanikoyes/godot,vnen/godot,Valentactive/godot,okamstudio/godot,groud/godot,DmitriySalnikov/godot,MarianoGnu/godot,vnen/godot,groud/godot,guilhermefelipecgs/godot,Zylann/godot,okamstudio/godot,DmitriySalnikov/godot,josempans/godot,DmitriySalnikov/godot,ZuBsPaCe/godot,okamstudio/godot,Zylann/godot,Shockblast/godot,n-pigeon/godot,ZuBsPaCe/godot,zicklag/godot,Valentactive/godot,mcanders/godot,sanikoyes/godot,okamstudio/godot,okamstudio/godot,groud/godot,Valentactive/godot,ZuBsPaCe/godot,MarianoGnu/godot,n-pigeon/godot,Faless/godot,groud/godot,mcanders/godot,vkbsb/godot,Shockblast/godot,sanikoyes/godot,honix/godot,ZuBsPaCe/godot,guilhermefelipecgs/godot,godotengine/godot,Shockblast/godot,ageazrael/godot,Brickcaster/godot,Zylann/godot,mcanders/godot,akien-mga/godot,guilhermefelipecgs/godot,Brickcaster/godot,DmitriySalnikov/godot,firefly2442/godot,Faless/godot,DmitriySalnikov/godot,pkowal1982/godot,pkowal1982/godot,NateWardawg/godot,pkowal1982/godot,Paulloz/godot,RandomShaper/godot,FateAce/godot,BastiaanOlij/godot,Paulloz/godot,vkbsb/godot,josempans/godot,okamstudio/godot,ageazrael/godot,ZuBsPaCe/godot,vnen/godot,n-pigeon/godot,FateAce/godot,NateWardawg/godot,Valentactive/godot,zicklag/godot,okamstudio/godot,RandomShaper/godot,guilhermefelipecgs/godot,NateWardawg/godot,mcanders/godot,akien-mga/godot,firefly2442/godot,firefly2442/godot,Valentactive/godot,Faless/godot,josempans/godot,Faless/godot,MarianoGnu/godot,ex/godot,vnen/godot,sanikoyes/godot,groud/godot,Valentactive/godot,akien-mga/godot,NateWardawg/godot,akien-mga/godot,ex/godot,NateWardawg/godot,zicklag/godot,pkowal1982/godot,honix/godot,Paulloz/godot,DmitriySalnikov/godot,ex/godot,RandomShaper/godot,ageazrael/godot,ageazrael/godot,n-pigeon/godot,FateAce/godot,Zylann/godot,godotengine/godot,BastiaanOlij/godot,BastiaanOlij/godot,ageazrael/godot,honix/godot,pkowal1982/godot,groud/godot,MarianoGnu/godot,Zylann/godot,ex/godot,DmitriySalnikov/godot,jejung/godot,RandomShaper/godot,MarianoGnu/godot,n-pigeon/godot,NateWardawg/godot,firefly2442/godot,firefly2442/godot,firefly2442/godot,NateWardawg/godot,MarianoGnu/godot,godotengine/godot,zicklag/godot,zicklag/godot,josempans/godot,godotengine/godot,n-pigeon/godot,honix/godot,Zylann/godot,vkbsb/godot,MarianoGnu/godot,jejung/godot,BastiaanOlij/godot,mcanders/godot