clang-format: Option to control spacing in template argument lists.

Same as SpacesInParentheses, this option allows adding a space inside
the '<' and '>' of a template parameter list.

Patch by Christopher Olsen.

This fixes llvm.org/PR17301.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@193614 91177308-0d34-0410-b5e6-96231b3b80d8