Update c_types.h to use stdbool
esp8266: Change makefile to be less position dependant.

The Makfile now supports giving it a bung of environment variables.
Fixed makefile for linking against SDK v0.9.3
Now building against fixed SDK 0.9.3

see https://github.com/jaseg/espressif-esp8266-sdk
Minor fixes

Fix accidentally reversed diff, revert usage of true/false, fix path to SDK example, bump SDK version in XCode project and readme.