6249704 exstr fails to close file descriptor

Summary:
All comments in bug apply.

Patch:
http://icculus.org/~eviltypeguy/6249704.patch

Lint/cstyle Patch (must be applied after original patch):
http://icculus.org/~eviltypeguy/6249704_lint.patch

Solution:
The solution was to explicitly close the filehandle used by the replace() at the very end of the function.

Testing:
The new exstr binary was tested on a SX build 16 system by using dmake to build it as an individual component from the first release of ON source tree. I tested the new exstr binary that I generated by using the examples for replace() as documented in the exstr manpage. The results from the new binary were the same as those listed in the manpage for the replace() example. This applies to both the original patch, and after applying the "lint" patch.