This reverts commit 1d73b52f5ba4184de6acf474f14668001304a10c
(Add string-specific memory pool, 2010-08-09). Now that svn-fe
does not need to maintain a growing collection of strings (paths)
over a long period of time, the string_pool is not needed.
Signed-off-by: David Barr <david.barr@cordelta.com> Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>