STM32 support in vsprog

Information:
    Vsprog can support STM32 in JTAG/SWD/COM ISP interfaces. And for COM ISP interface, you can use a generic COM port on your PC, or you can select usbtocomm if USB_TO_USART is enabled in USB_TO_XXX protocol.
    Auto-detect feature is supported on STM32.
    Supported target area: flash('f').

Vsprog options:
    -sstm32, refer to -s option.
    -c, refer to -c option. Supported chips:
        stm32_ld: Low Denesity
        stm32_md: Medium Denesity
        stm32_hd: High Denesity
        stm32_conn: Connectivity Line
        stm32_vl: Value Line
    -m, refer to -m option. Supported modes:
        i: USART ISP mode
        j: JTAG mode, default
        s: SWD mode
    -C, refer to -C option. This option is only valid in USART ISP mode.
    -F, refer to -F option. This option is only valid in JTAG mode, default is 8000 / 6, unit: kHz.
    -W, refer to -W option. This option is only valid in SWD mode, default is 0. It defines the speed of SWD, the lower the value the faster the speed. Normally, default value is OK.
    -x, refer to -x option.