use fmtprint to avoid va_copy

src/libbio/bprint.c

diff --git a/src/libbio/bprint.c b/src/libbio/bprint.c
index f8a4d94..878bfb6 100644
--- a/src/libbio/bprint.c
+++ b/src/libbio/bprint.c
@@ -10,11 +10,7 @@
 
 	if(Bfmtinit(&f, bp) < 0)
 		return -1;
-	va_start(args, fmt);
-	va_copy(f.args, args);
-	n = dofmt(&f, fmt);
-	va_end(args);
-	va_end(f.args);
+	n = fmtprint(&f, fmt, args);
 	if(n > 0 && Bfmtflush(&f) < 0)
 		return -1;
 	return n;