The M114 unconditionally prints "X:" and the number. M119 has this code:
Code:
    case 119: // M119
    SERIAL_PROTOCOLLN(MSG_M119_REPORT);
      #if defined(X_MIN_PIN) && X_MIN_PIN > -1
        SERIAL_PROTOCOLPGM(MSG_X_MIN);
        SERIAL_PROTOCOLLN(((READ(X_MIN_PIN)^X_MIN_ENDSTOP_INVERTING)?MSG_ENDSTOP_HIT:MSG_ENDSTOP_OPEN))
If the M119 command prints that stuff correctly, it uses the same SERIAL_PROTOCOLPGM() macro.