import-checker: use testparseutil.embedded() to centralize detection logic This patch fixes issues of embedded() in import-checker.py below, too. - overlook (or mis-detect) the end of inline script in doctest style - overlook inline script in doctest style at the end of file (and ignore invalid un-closed heredoc at the end of file, too) - overlook code fragment in styles below - "python <<EOF" (heredoc should be "cat > file <<EOF" style) - "cat > foobar.py << ANYLIMIT" (limit mark should be "EOF") - "cat << EOF > foobar.py" (filename should be placed before limit mark) - "cat >> foobar.py << EOF" (appending is ignored)