cosmetic changes + enter behavior (#126)

* remove trailing whitespace

* always submit password on enter

Moves the keypress logic for keypresses from if-else statements
to switches, adds non-contextual behavior on pressing enter

* wrap pam actions and handle errors at on spot

* init all of text struct in input_text()

This gets rid off valgrind warning on unitialized variables

src/config.c

@@ -263,7 +263,7 @@ void config_defaults()
 	config.blank_box = true;
 	config.blank_password = false;
 	config.console_dev = strdup("/dev/console");
-	config.default_input = 2;
+	config.default_input = PASSWORD_INPUT;
 	config.fg = 9;
 	config.hide_borders = false;
 	config.input_len = 34;