Buttons: small optimization for vector

code/espurna/button.ino

@@ -159,12 +159,16 @@ void buttonSetup() {
 
     #if defined(ITEAD_SONOFF_DUAL)
 
+        _buttons.reserve(3);
+
         buttonAdd(GPIO_NONE, BUTTON_PUSHBUTTON, 0, _buttonRelay(0));
         buttonAdd(GPIO_NONE, BUTTON_PUSHBUTTON, 0, _buttonRelay(1));
         buttonAdd(GPIO_NONE, BUTTON_PUSHBUTTON, 0, _buttonRelay(2));
 
     #elif defined(FOXEL_LIGHTFOX_DUAL)
 
+        _buttons.reserve(4);
+
         const auto actions = _buttonConstructActions(
             BUTTON_MODE_NONE, BUTTON_MODE_TOGGLE, BUTTON_MODE_NONE,
             BUTTON_MODE_NONE, BUTTON_MODE_NONE, BUTTON_MODE_NONE
@@ -208,6 +212,8 @@ void buttonSetup() {
             ++buttons;
         #endif
 
+        _buttons.reserve(buttons);
+
         // TODO: load based on index
         button_t::DebounceDelay = getSetting("btnDebounce", BUTTON_DEBOUNCE_DELAY);
         button_t::DblclickDelay = getSetting("btnDelay", BUTTON_DBLCLICK_DELAY);