Fix a windows build issue

Fix a windows build issue

../../dart/runtime/vm/flags.cc:58:26: error: invalid suffix on literal; C++11 requires a space between literal and identifier [-Wreserved-user-defined-literal]
        OS::Print("%s: %"Pu64" (%s)\n", name_, *this->uint64_ptr_, comment_);

R=regis@google.com

Committed: https://code.google.com/p/dart/source/detail?r=43669

[siva, 2015-02-10 21:00:57]

asiva@google.com changed reviewers:
+ regis@google.com

[regis, 2015-02-10 21:16:19]

LGTM

Thanks for fixing.

[siva, 2015-02-10 21:30:38]

Committed patchset #1 (id:1) manually as r43669 (presubmit successful).