This test case is originally made for testing the change proposed in
#2268. However, it doesn't verify the behavior affected by the change.

In Postgresql, "is" can be used as a function name.  In many of the
other SQL DB implementations, "is" is a reserved word, Therefore, "is"
cannot be used as a function name.

When SQL parser of ctags reads a SQL input file, it doesn't care
whether an identifier appearing at the position where a function name
is expected is a reserved word or not. Therefore, the change proposed
in #2268 has no impact on the way to capture function name.

