fix(parser): parse ABI markers and keep TEXT decls usable on errors

Assisted-by: GLM 5.3

ast/ast.go

@@ -114,6 +114,7 @@ type Symbol struct {
 	Pkg    string // package prefix before the middle dot ("" = current package)
 	Name   string // identifier without the middle dot or <>
 	Static bool   // the <> marker is present
+	ABI    string // the <NAME> ABI marker, e.g. ABIInternal ("" when absent)
 	Pseudo string // FP, SP, SB or PC ("" for a bare name)
 	Offset int64
 	HasOff bool
@@ -156,5 +157,5 @@ type Address struct {
 	Scale  int     // index scale; 0 when absent
 	Offset int64   // leading displacement, from off(base)
 	HasOff bool    // a leading displacement is present
-	Shift  string  // verbatim arm64 shift suffix, e.g. "<<2"
+	Shift  string  // verbatim arm64 shift suffix, e.g. "<< 2"
 }