1. Add pwm support;
2. Add c++ support; Please update to the latest folder "ld".
3. Add rand in libminic;
4. Add new reset reason REASON_EXT_SYS_RST in rst_reason;
5. Update the complied script ‘gen_misc.sh(bat)’, use the new boot and remove the old one;
6. Update folder "tools", and support CRC check of bin files; Please update to the latest folder "tools".
7. Optimize the process procedure of Wi-Fi event;
8. Fix bugs in printf when its runs out of memory;
9. Fix bugs in malloc when CACHE is disabled;
10.Fix exception and WDT reset bugs when CACHE is disabled;
11.Fix some Wi-Fi connection bugs;
12.Fix some Wi-Fi scan bugs;
13.Tune API "wifi_station_get_connect_status" for more accurate WiFi positioning;
14.Porting the optimization of non-OS SDK to RTOS SDK;
15.Fix other minor bugs.
