Merge branch 'master' into feature/dualcore_spi_flash_api

Merge branch 'master' into feature/dualcore_spi_flash_api

* master: (130 commits)
  lwip: Define LWIP_ESP8266 in port lwipopts.h not gcc command line
  CI: Build the esp-idf-template with the matching branch name, if it exists
  README: Add Resources section with some links
  Rename README.buildenv to docs/build_system.rst and ReST-ify it
  Eclipse docs: Easier to just replace entire PATH, msys32 has everything we need to build/flash
  test_build_system: Print ESP_IDF_TEMPLATE_GIT for easier debugging
  Name component makefiles component.mk instead of Makefile
  Eclipse doc: Add troubleshooting note about Makefile directories
  eclipse_make.sh: Fix printing of make directory
  Move bin/eclipse_windows_make.sh to tools/windows_eclipse_make.sh
  Eclipse docs: Prepend IDF paths to beginning of PATH
  Set default SPI flash access mode to DIO
  FreeRTOS: temporary solution for memory canaries and memory debug
  tcpip_adapter: fix dhcp client work flow
  event: not post got ip event if static is invalid
  tcpip_adapter: typedef clean up
  event: post got ip event when use static ip
  tcpip_adapter: use dhcp callback to post got ip event
  dhcp: add dhcp callback
  lwip: remove netif_reg_addr_change_cb
  ...