Allow absence of i64 suffix when __int64 exists.

The dashboard showed a compile failure on icc because the i64 suffix
did not exist, even though cmake had detected __int64. This patch uses
a suffix of either l or ll if __int64 is really 'long' or 'long long'.

Change-Id: I69b90821d25e4937e22bfc9bf63faaeae9472030
Merge topic 'missing-suffix-i64' into master

ef02d785 Allow absence of i64 suffix when __int64 exists.