selfhost: graduate SK_* defs to skind enum

lib/ww/sym.ww

@@ -9,14 +9,16 @@ use typ;
 use ast;
 
 // Symbol kinds — must stay numerically aligned with cmd/wcc/ww.h Skind.
-def SK_NONE:  i32 = 0;
-def SK_VAR:   i32 = 1;
-def SK_PARAM: i32 = 2;
-def SK_DEF:   i32 = 3;
-def SK_TYPE:  i32 = 4;
-def SK_FN:    i32 = 5;
-def SK_USE:   i32 = 6;
-def SK_FIELD: i32 = 7;
+type skind = enum i32 {
+	SK_NONE  = 0,
+	SK_VAR   = 1,
+	SK_PARAM = 2,
+	SK_DEF   = 3,
+	SK_TYPE  = 4,
+	SK_FN    = 5,
+	SK_USE   = 6,
+	SK_FIELD = 7,
+};
 
 type sym = struct {
 	name:     str,