Fix -Wmissing-field-initializers warnings in gcc 4.9
Fix -Wmissing-field-initializers warnings in gcc 4.9

The previous method of initialisation was correct for c++11
but GCC 4.9 gives false positives about it.
For more information see:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61489

realm/realm-core,realm/realm-core,realm/realm-core,realm/realm-core,realm/realm-core,realm/realm-core,realm/realm-core