Add sha1sum

No support for -c at the moment.

sha1.h

@@ -0,0 +1,18 @@
+/* public domain sha1 implementation based on rfc3174 and libtomcrypt */
+
+struct sha1 {
+	uint64_t len;    /* processed message length */
+	uint32_t h[5];   /* hash state */
+	uint8_t buf[64]; /* message block buffer */
+};
+
+enum { SHA1_DIGEST_LENGTH = 20 };
+
+/* reset state */
+void sha1_init(struct sha1 *s);
+/* process message */
+void sha1_update(struct sha1 *s, const void *m, unsigned long len);
+/* get message digest */
+/* state is ruined after sum, keep a copy if multiple sum is needed */
+/* part of the message might be left in s, zero it if secrecy is needed */
+void sha1_sum(struct sha1 *s, uint8_t md[SHA1_DIGEST_LENGTH]);