h5edit

Portability fixes:
1. SunOS' native tail does not support -n. Changed to use sed to do filtering.
2. "==" is not legal for SunOS' test command. Changed to "=".

Tested: jam, koala, linew, ostrich, duck, wren. All passed.

Added Mac OS X 10.7.5 and 10.8.2 to the list of supported platforms.