arduino spec implementation

[apla]

Arduino is actually a specification.

Workflow as see-the-source spec:

1. all .ino/.pde is concatenated together (not sure about feature usability)
2. resulting file is preprocessed (insert #include "Arduino.h" just before first statement)
3. add folders to compiler includes by header name (see Arduino user libraries not found brackets-cuwire#10) — cada84c
4. compile cores and variants, make archive
5. compile every .c/.cpp file in libraries
6. compile every .c/.cpp file in project
7. link all together
8. check size

Actual specifications:

1. 3rd party hardware spec not fully implemented
   • support alias in boards. guide — 02ea24b

Hacks as specifications:

1. platform.local.txt to override value in platform.txt
2. reading arduino preferences (mine is ~/Library/Arduino15/preferences.txt) — at least sketchbook folder