PdePreprocessor restored to version 316b871
Added an "insideString" flag in scrubComments to avoid failing with strings like "Hello */*"
Added a handful of tests taking code from various issues in order to better avoid future regressions
Closes #1687
Enforcing string start/end check. See #1687
Preprocessor regexp: "." now matches even line terminators. Closes #1653
Fixed non working example: StringStartsWithEndsWith.ino
PreProcessor now replace every single char with a space, without collapsing multiline matches
Fixed compile error on StandardFirmata example.

Revert "Servo library refactoring. See #1617"

This reverts commit e8834d32f3f09cf6ce9a52bd30ba552bcb8291ef.

See #1617
Don't forbid unknown files in a library

The current code forbids any files it does not know about, but this is
bad because:
 - It breaks forward compatibility if we later add more files or
   directories to the library format.
 - It breaks for people who want to have some extra stuff in their
   library (say, .gitignore or a README file). We can't keep a list of
   "allowed" stuff, since there will always be stuff missing.

This commit removes that code and just allows all files again.
Reintroduced warning on development leftovers in 1.5 libraries.

See #1692