- Move macro definition to mbed_toolchain.h
- Remove double underscores from macro which are reserved.
- Fix macro for IAR until compiler flags to disable path are added again.
Existing ATParser is extended to use FileHandle. This essentially detaches
ATParser from previous tight binding with various implementations of serial
interfaces with buffering.
Now the ATParser uses only abstract FileHandle and doesn't really care about
the underlying implementation. Underneath, it could be a USB device type FileHandle
or a Serial device type FileHandle etc.
Some simplification steps were taken as the code provided opportunities to simplify
and optimize.