2.3.0-rc1

Core

• Fix NMI interrupt handler alignment
• Update SDK to 1.5.3
• umm_malloc: print block start address before heap corruption callback is triggered
• If GDBStub library is used, break into gdb on assert and panic

Libraries

• SNI support in WiFiClientSecure (#1285)
• Update axTLS to 139914f
• HTTPClient: return error when HTTPClient::begin is called with HTTPS URL without certificate fingerprint (#1941)
• HTTPClient: fix default port not being set
• HTTPClient: fix handling of chunked transfer encoding (#1975)
• ESP8266SSDP: switch SSDP send arguments around
• ESP8266WiFi: fix UdpContext::peek to return int (#1946)
• ESP8266WiFi: fix WiFiSleepType_t values to match SDK ones
• LwIP: use gcc-built LwIP by default (#1926)
• LwIP: fix crash in igmp_start_timer (#1826)
• HTTPClient: include non-standard ports in Host: header
• ESP8266WiFi: Prevent WiFi config corruption (#1997 #1856 #1699 #1675)
• GDBStub: fix section attribute for core gdbstub functions

Tools

• Python 3 compatibility for get.py
• Device side test library and test runner
• Fix ARM toolchain files permissions (#2004)