Converting floats to doubles is very expensive on esp8266, so prefer
calculations or comparisons as float. This saves 10% (20 bytes) of the
String::parseFloat() code size and probably quite a bit of runtime
overhead.
This includes empty stubs for most core Arduino functions.
Need to actually implement all those digital reads writes whatever.
Need to prebuild toolchains (xtensa-elf-lx106) for 3 platforms and put them on some download server.
Need to do the same with esptool.
Need to fix 0x40000 binary generation and add correct upload commands.
Maybe even implement uploads over WiFi.
