Renamed the main linker script to make it clear it is customised for NodeMCU
and not to be confused with the standard linker SDK linker scripts.
Changed to using the eagle.rom.addr.v6.ld file from the SDK.
Accessing 8bit and 16bit constants from ROM rather than RAM comes with a
performance cost, as these loads go through the load/store exception
vector. Any performance critical constants can be forced back into RAM
as RAM_CONST_ATTR.
The entry point has changed from call_user_start() to user_start_trampoline()
in order for the exception handler to be installed early enough.
The open source LWIP is broken, use espressif's liblwip.a.
Uses system_get_vdd33 instead of readvdd33.
The espressif's sdk0.9.6 beta1 (2015.02.15) release note
1、Optimize smartconfig to version v0.8;
2、Optimize AT to version 0.22.b1;
1>、Fixed bugs;
2>、Optimize the speed of transparent transmission;
3、Optimize boot to version 1.3(b3);
1>、Fix compatibility problem of dual flash ;
4、Solve problem of the large current in deep sleep;
5、Fixed problem “check mem fail”;
6、Fixed problem of UDP socket may stop listening broadcast packet after a long time running under some special router;
7、Fixed bug related to wifi_station_scan;
8、Other optimize to make the software more reliable;
* macros established to build a table of fonts which get compiled into the image
* font data is mapped to irom0 to save dram space
* quirky function to retrieve font data 4-byte aligned from irom0