Replace ukbhit by kbd_enter_pressed, not requiring tcgetattr:

Note that it behaves differently now
* it looks for Enter key only, not any key
* it "eats" the input, no need for (void)getchar() after it
* it works the same no matter the value of ICANON
* the mingw version has been adapted to act the similarly

This should fix its usage on Android where tcgetattr always returns -1

client/lualibs/hf_reader.lua

@@ -15,10 +15,10 @@ local reader15693 = require('read15')
 -- @return if successfull: an table containing card info
 -- @return if unsuccessfull : nil, error
 local function waitForTag()
-    print("Waiting for card... press any key to quit")
+    print("Waiting for card... press Enter to quit")
     local readers = {reader14443A, reader14443B, reader15693}
     local i = 0;
-    while not core.ukbhit() do
+    while not core.kbd_enter_pressed() do
         i = (i % 3) +1
         r = readers[i]
         print("Reading with ",i)