PollyDectect: Use spaces before foreach colons

clang-format requires a space before the ":" in the foreach loop. Even though
this is surprising to me, we follow this style to make our formatting
consistent with clang-format. I found that this clang-format style is used in a
couple of C++11 examples, hence I believe the fact that clang-format adds a
colon is not a bug but just something I was not used to yet.

git-svn-id: https://llvm.org/svn/llvm-project/polly/trunk@202648 91177308-0d34-0410-b5e6-96231b3b80d8