[PATCH] Improve the regex of sed command of SVN_SERF_INCLUDES macro

Hello,.

When calculate SVN_SERF_INCLUDES macro in serf.m4, it removes any '-D'
in string. If $serf_major was installed
into directory with '-D' in its path, such as "My-Demo", then get wrong
value of SVN_SERF_INCLUDES.

[[[
Improve the regex of sed command of SVN_SERF_INCLUDES macro

The regex of sed command is too simple, which mangles any "-D"
in strings, for example, a path name is "My-Demo", it will be removed
from the path by the sed regex, which causes a build failure. Improving
it to only delete the -D behind of a space or the -D at start of a string.
]]]

-- 
Regards,
Neil | Kai Kang