Catch our explicit EOF 0x04

We pass in `"\x04"` as an EOF character in our tests, so let's ensure
that we handle that as an EOF in `getpass()`.

base/util.jl

@@ -266,7 +266,7 @@ function getpass(input::TTY, output::IO, prompt::AbstractString)
     plen = 0
     while true
         c = _getch()
-        if c == 0xff || c == UInt8('\n') || c == UInt8('\r')
+        if c == 0xff || c == UInt8('\n') || c == UInt8('\r') || c == 0x04
             break # EOF or return
         elseif c == 0x00 || c == 0xe0
             _getch() # ignore function/arrow keys