add support for AVR

this need some more testing but basics are done

src/libsha1/libsha1.h

@@ -0,0 +1,21 @@
+/* ================ sha1.h ================ */
+/*
+SHA-1 in C
+By Steve Reid <steve@edmweb.com>
+100% Public Domain
+*/
+
+#ifndef ESP8266
+
+typedef struct {
+    uint32_t state[5];
+    uint32_t count[2];
+    unsigned char buffer[64];
+} SHA1_CTX;
+
+void SHA1Transform(uint32_t state[5], const unsigned char buffer[64]);
+void SHA1Init(SHA1_CTX* context);
+void SHA1Update(SHA1_CTX* context, const unsigned char* data, uint32_t len);
+void SHA1Final(unsigned char digest[20], SHA1_CTX* context);
+
+#endif