cppmagic: Tweak testcase to work on older clang versions

clang version 3.4, for whatever reason, expands a few of the testcases
in cppmagic with slightly different whitespace from what we expect.  Since
this was changed in later clang versions, it was probably a compiler bug,
but it turns out an extra space in the testcase can make it pass on clang
3.4 as well.  This means we finally have clang builds working in Travis.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>