svnexternals: fix subrepo peg revision handling (7ef125fa9b35) hg >= 1.9 appends the revision to check out as a peg revision to source URL before calling svn. This breaks the case where the external definition already contains a peg revision. Instead, we assume that "-rR1 svnurl@R2" is equivalent to "svnurl@R1" which should be almost always true in practice. The import test has been reversed to avoid issues with stray .pyc: if you install an hg 1.8 over an hg 1.9, scmutil.pyc may remain and be imported, while util.py exists in both cases.