Small changes to get eyre to build on Ubuntu 10.04

[dhruvbansal]

I couldn't get eyre to build for me on Ubuntu 10.04 so I made a few tweaks:

• The Makefile now sets the default include directly based on the value of OS
• Time comparisons are done in a few places using modification times from calls to stat. Code as written wasn't portable to Linux b/c of use of st_mtimespec which is only defined on BSD. Used a macro that checks the value of OS and appropriately uses either st_mtimespec or st_mtime
• Added a few files to .gitignore

Eyre now builds and starts...and then segfaults immediately. But first things first -- I've got it running, yay!