remove enable/disable; use bitlfags objects instead

Simplifies the interface, less methods

examples/password_input.lua

@@ -16,14 +16,14 @@ local function read_secret(...)
 
   if sys.isatty(io.stdin) then
     -- backup settings, configure echo flags
-    w_oldflags = sys.disableconsoleflags(io.stdin, sys.CIF_ECHO_INPUT)
+    w_oldflags = sys.getconsoleflags(io.stdin)
     p_oldflags = sys.tcgetattr(io.stdin)
-    sys.tcdisableattr(io.stdin, sys.TCSANOW, {
-      lflag = sys.L_ECHO, -- echo is off to not show password on screen
-    })
-    sys.tcenableattr(io.stdin, sys.TCSANOW, {
-      lflag = sys.L_ECHONL, -- echo is off, but we still echo the final newline
-    })
+    -- Windows: echo is off to not show password on screen (has no L_ECHONL option)
+    assert(sys.setconsoleflags(io.stdin, w_oldflags - sys.CIF_ECHO_INPUT))
+    -- Posix: echo is off to not show password on screen, but we still echo the final newline
+    assert(sys.tcsetattr(io.stdin, sys.TCSANOW, {
+      lflag = p_oldflags.lflag - sys.L_ECHO + sys.L_ECHONL
+    }))
   end
 
   local secret, err = io.stdin:read(...)

src/bitflags.h

@@ -11,6 +11,7 @@
 
 // Validates that the given index is a bitflag object and returns its value.
 // If the index is not a bitflag object, a Lua error is raised.
+// The value will be left on the stack.
 LSBF_FLAGTYPE lsbf_checkbitflags(lua_State *L, int index);
 
 // Pushes a new bitflag object with the given value onto the stack.

src/core.c

@@ -33,10 +33,10 @@ LUAEXPORT int luaopen_system_core(lua_State *L) {
     lua_pushboolean(L, 0);
 #endif
     lua_rawset(L, -3);
+    bitflags_open(L); // must be first, used by others
     time_open(L);
     random_open(L);
     term_open(L);
     environment_open(L);
-    bitflags_open(L);
     return 1;
 }