fix build of gflags on some compilers

* C++11 requires a space between literal and identifier

Change-Id: I8ac2f8b55da069189d52d1ea1e0d6e98a1db2b38
Signed-off-by: liuhuahang <liuhuahang@xiaomi.com>
Merge pull request #8 from huahang/chen3feng/master

fix build of gflags on some compilers