Data: fix various typos

Found via `codespell -q 3 -S "./Externals,./Data/Sys/wiitdb-??.txt,*.po,*.pot" -L andf,asnd,bootup,brocken,bufferin,clen,collet,datas,delt,diety,extint,fpr,inout,inport,interm,nd,nin,ontop,pixelx,re-use,re-used,sav,stateman,strat,transer,wil`

Data/Sys/Shaders/nightvision2.glsl

@@ -40,7 +40,7 @@ void main()
 
 	/*****inline square root routines*****/
 	// bit of a performance bottleneck.
-	// neccessary to make the darkened area rounded
+	// necessary to make the darkened area rounded
 	// instead of rhombus-shaped.
 	float sqrt = x / 10.0;