use new strconv API

All but 3 cases (in gcimporter.go and hixie.go)
are automatic conversions using gofix.

No attempt is made to use the new Append functions
even though there are definitely opportunities.

R=golang-dev, gri
CC=golang-dev
https://golang.org/cl/5447069
diff --git a/src/pkg/debug/elf/elf.go b/src/pkg/debug/elf/elf.go
index c71b230..03e42b0 100644
--- a/src/pkg/debug/elf/elf.go
+++ b/src/pkg/debug/elf/elf.go
@@ -1490,11 +1490,11 @@
 			if goSyntax {
 				s = "elf." + s
 			}
-			return s + "+" + strconv.Uitoa64(uint64(i-n.i))
+			return s + "+" + strconv.FormatUint(uint64(i-n.i), 10)
 		}
 	}
 
-	return strconv.Uitoa64(uint64(i))
+	return strconv.FormatUint(uint64(i), 10)
 }
 
 func flagName(i uint32, names []intName, goSyntax bool) string {
@@ -1512,10 +1512,10 @@
 		}
 	}
 	if len(s) == 0 {
-		return "0x" + strconv.Uitob64(uint64(i), 16)
+		return "0x" + strconv.FormatUint(uint64(i), 16)
 	}
 	if i != 0 {
-		s += "+0x" + strconv.Uitob64(uint64(i), 16)
+		s += "+0x" + strconv.FormatUint(uint64(i), 16)
 	}
 	return s
 }