Moved all src files into the src directory

Also fixed the "isNetworkConnected" for ESP8266

src/TinyGsmFifo.h

@@ -0,0 +1,136 @@
+#ifndef TinyGsmFifo_h
+#define TinyGsmFifo_h
+
+template <class T, unsigned N>
+class TinyGsmFifo
+{
+public:
+    TinyGsmFifo()
+    {
+        clear();
+    }
+
+    void clear()
+    {
+        _r = 0;
+        _w = 0;
+    }
+
+    // writing thread/context API
+    //-------------------------------------------------------------
+
+    bool writeable(void)
+    {
+        return free() > 0;
+    }
+
+    int free(void)
+    {
+        int s = _r - _w;
+        if (s <= 0)
+            s += N;
+        return s - 1;
+    }
+
+    bool put(const T& c)
+    {
+        int i = _w;
+        int j = i;
+        i = _inc(i);
+        if (i == _r) // !writeable()
+            return false;
+        _b[j] = c;
+        _w = i;
+        return true;
+    }
+
+    int put(const T* p, int n, bool t = false)
+    {
+        int c = n;
+        while (c)
+        {
+            int f;
+            while ((f = free()) == 0) // wait for space
+            {
+                if (!t) return n - c; // no more space and not blocking
+                /* nothing / just wait */;
+            }
+            // check free space
+            if (c < f) f = c;
+            int w = _w;
+            int m = N - w;
+            // check wrap
+            if (f > m) f = m;
+            memcpy(&_b[w], p, f);
+            _w = _inc(w, f);
+            c -= f;
+            p += f;
+        }
+        return n - c;
+    }
+
+    // reading thread/context API
+    // --------------------------------------------------------
+
+    bool readable(void)
+    {
+        return (_r != _w);
+    }
+
+    size_t size(void)
+    {
+        int s = _w - _r;
+        if (s < 0)
+            s += N;
+        return s;
+    }
+
+    bool get(T* p)
+    {
+        int r = _r;
+        if (r == _w) // !readable()
+            return false;
+        *p = _b[r];
+        _r = _inc(r);
+        return true;
+    }
+
+    int get(T* p, int n, bool t = false)
+    {
+        int c = n;
+        while (c)
+        {
+            int f;
+            for (;;) // wait for data
+            {
+                f = size();
+                if (f)  break;        // free space
+                if (!t) return n - c; // no space and not blocking
+                /* nothing / just wait */;
+            }
+            // check available data
+            if (c < f) f = c;
+            int r = _r;
+            int m = N - r;
+            // check wrap
+            if (f > m) f = m;
+            memcpy(p, &_b[r], f);
+            _r = _inc(r, f);
+            c -= f;
+            p += f;
+        }
+        return n - c;
+    }
+
+private:
+    int _inc(int i, int n = 1)
+    {
+        return (i + n) % N;
+    }
+
+    T    _b[N];
+    int  _w;
+    int  _r;
+};
+
+#endif