* bsp beaglebone: rerun menuconfg

* bsp beaglebone: add uart0 support

* bsp beaglebone: use uart0 as console

* bsp beaglebone: add heap init

fix rt_application_init() error:
(m != RT_NULL) assertion failed at function:rt_smem_alloc, line number:288

* bsp beaglebone: add mmu & interrupt init

must init mmu, otherwise no interrupt is generated, cause scheduler can't work.
I don't know why need mmu, just seen: bsp/rockchip/rk3568/driver/board.c

* libcpu am335x: reset interrupt controller before init vector

I think reset before init is more better

AM335X_StarterWare_02_00_01_01\system_config\armv7a\am335x\interrupt.c
IntAINTCInit()

* bsp beaglebone: full gpio driver support

* bsp beaglebone: add tftpboot way to uboot_cmd.txt

* bsp beaglebone: optimize am33xx_gpio_hdr, check irqstatus is the last one
Co-authored-by: YangZhongQing <vipox@qq.com>

1. SConstruct中增加对C++支持
2. 重新menuconfig. 删除application.c/startup.c,增加main.c. 以便通过编译

add rt_console_set_devic，components,gpio,rtc