Add crypt.[ch] and update md5sum and sha1sum

Factor out the code from md5sum and sha1sum into a util function.

Use FILE * instead of a file descriptor.  This will make it a bit
easier/more consistent when we implement support for the -c option.

util/crypt.c

@@ -0,0 +1,33 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include "../util.h"
+#include "../crypt.h"
+
+int
+cryptsum(struct crypt_ops *ops, FILE *fp, const char *f,
+	 uint8_t *md)
+{
+	unsigned char buf[BUFSIZ];
+	size_t n;
+
+	ops->init(ops->s);
+	while ((n = fread(buf, 1, sizeof(buf), fp)) > 0)
+		ops->update(ops->s, buf, n);
+	if (ferror(fp)) {
+		eprintf("%s: read error:", f);
+		return 1;
+	}
+	ops->sum(ops->s, md);
+	return 0;
+}
+
+void
+mdprint(const uint8_t *md, const char *f, size_t len)
+{
+	size_t i;
+
+	for (i = 0; i < len; i++)
+		printf("%02x", md[i]);
+	printf("  %s\n", f);
+}