because "svnversion" may emit a version number with ":" in it (duh!).
This fixes the problem where, depending on the status of your svn
checkout, you could get a string in a MAJOR version number instead of
an integer (i.e., "1234M" instead of "10"). This was caused by
extraneous ":" in the output, causing autogen.sh to grab the wrong
field.
This commit was SVN r1991.