Add Serial.buffer() and Serial.bufferUntil() functions. [imported]

This is [Issue 535](http://code.google.com/p/arduino/issues/detail?id=535) moved from a Google Code project.
Added by 2011-05-07T17:10:42.000Z by [dmel...@gmail.com](http://code.google.com/u/107726014984682000895/).
Please review that bug for more context and additional comments, but update this bug.

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

These should be along the lines of the Processing equivalents, triggering the corresponding serialEvent() functions when the particular character or number of characters is read.