w6c: append() accepts struct CALL rvalue elements (#34)

Evaluate the call pre-grow into a per-site scratch, receiving by the
N_LET matrix (sret / float / odd-tail / GP), then grow, slot, sized
ladder. Both stages, byte-identical. The two reject pins graduate to
16B GP accept rows; three new fixtures cover 24B GP, 3B/4B tails,
16B float, and 40B sret.

internal/wwfixture/types.ww

@@ -1,13 +1,13 @@
 package wwfixture;
 
 def protocolversion: i32 = 1;
-def corpuscount: i32 = 1631;
-def errorcount: i32 = 338;
+def corpuscount: i32 = 1634;
+def errorcount: i32 = 336;
 def compilecount: i32 = 17;
 def runcount: i32 = 198;
-def runexitcount: i32 = 1078;
-def nativecount: i32 = 3262;
-def corpushash: str = "f1186d55d4f4a447de61b1246f8296c9f5996b406de36da0e5eb277fd2352e52";
+def runexitcount: i32 = 1083;
+def nativecount: i32 = 3268;
+def corpushash: str = "cb7cf09decc2f64b40c1f06b836c5b2aec0a4f1b9b2a78665f228606a0245a1f";
 
 type directive = enum i32 {
 	ERROR = 0,