adding support of code completion [imported]

This is [Issue 849](http://code.google.com/p/arduino/issues/detail?id=849) moved from a Google Code project.
Added by 2012-03-07T13:26:22.000Z by [Wilfried...@gmail.com](http://code.google.com/u/104914328976362983260/).
Please review that bug for more context and additional comments, but update this bug.

Original labels: Type-Enhancement, Priority-Medium
### Original description

**What change would like to see?**
I would like to see a code completion in the IDE like other IDE Editors have. Especially it would be nice, when this feature could interact with the #include keyword.

**Why?**
Because of simpler programming.

**Would this cause any incompatibilities with previous versions? If so, how**
**can these be mitigated?**
I thing, there will be no incompatibilities.

Start by reviewing the linked Google Code Issue 849 and the Arduino IDE 1.x codebase, focusing on the IDE's editing and #include behavior. Define completion behavior and its interaction with included code, then verify that the IDE provides useful code completion without incompatibilities.

Written by the indexing model from the issue text.