Expanding Include Files

[CarlC]

Here's a good one that maybe someone has already done.

If I am editting a main source file, I would like a function that would
expand my buffer to show the contents of "include" files. This doesn't have
to be for C, it could be any language. I would customize it for my own use.
I would like these external files to be in-line with the program that I am
editting. Preferably with read-only on these chunks. I would be able to
search and access any of this source as if it were one file, but I would
only edit and save the original code.

Any ideas on how/if this could be done. Thanks.