go/gcimporter: cut off any gc-specific parameter numbering

Matching pending CL https://golang.org/cl/22441/.

Change-Id: I96fab1da7abfeb8f22ce680183649dfa4b84d461
Reviewed-on: https://go-review.googlesource.com/22442
Reviewed-by: Alan Donovan <adonovan@google.com>

go/gcimporter15/bimport.go

@@ -15,6 +15,7 @@ import (
 	"go/token"
 	"go/types"
 	"sort"
+	"strings"
 	"unicode"
 	"unicode/utf8"
 )
@@ -508,6 +509,9 @@ func (p *importer) param(named bool) (*types.Var, bool) {
 		if name == "" {
 			panic("expected named parameter")
 		}
+		if i := strings.Index(name, "·"); i > 0 {
+			name = name[:i] // cut off gc-specific parameter numbering
+		}
 		pkg = p.pkg()
 	}