switch to go vendoring

vendor/github.com/aws/aws-sdk-go/internal/strings/strings.go

@@ -0,0 +1,11 @@
+package strings
+
+import (
+	"strings"
+)
+
+// HasPrefixFold tests whether the string s begins with prefix, interpreted as UTF-8 strings,
+// under Unicode case-folding.
+func HasPrefixFold(s, prefix string) bool {
+	return len(s) >= len(prefix) && strings.EqualFold(s[0:len(prefix)], prefix)
+}