Refactoring uart interface (#341)

* uart: Major cleanups
- Adds documentation to the uart API.
- Fixes a buffer overflow issue in `uart_receive`, where the maximum parameter was ignored.
- Splits the maximum length and bytes recieved variables in `uart_receive`.
- Downsizes the receive buffer to the minimum required, saving 16MiB of RAM at runtime.
- Refactors the POSIX and Win32 implementations of uart into separate files.
- Removes the unused `uart_{get,set}_parity` functions, which were not implemented on Win32.

client/flasher.c

@@ -19,6 +19,8 @@
 
 #ifdef _WIN32
 # define unlink(x)
+#else
+# include <unistd.h>
 #endif
 
 static serial_port sp;
@@ -52,8 +54,7 @@ void ReceiveCommand(UsbCommand* rxcmd) {
   byte_t* prx = prxcmd;
   size_t rxlen;
   while (true) {
-    rxlen = sizeof(UsbCommand) - (prx-prxcmd);
-    if (uart_receive(sp,prx,&rxlen)) {
+    if (uart_receive(sp, prx, sizeof(UsbCommand) - (prx-prxcmd), &rxlen)) {
       prx += rxlen;
       if ((prx-prxcmd) >= sizeof(UsbCommand)) {
         return;
@@ -129,7 +130,7 @@ int main(int argc, char **argv)
   
   fprintf(stderr,"Waiting for Proxmark to appear on %s",serial_port_name);
   do {
-    sleep(1);
+    msleep(1000);
     fprintf(stderr, ".");
   } while (!OpenProxmark(0));
   fprintf(stderr," Found.\n");