pgsql: Cast to void in StaticAssertExpr, not its callers.

Cast to void in StaticAssertExpr, not its callers.

Seems a bit silly that many (in fact all, as of today) uses of
StaticAssertExpr would need to cast it to void to avoid warnings from
pickier compilers.  Let's just do the cast right in the macro, instead.

In passing, change StaticAssertExpr to StaticAssertStmt in one
place where that seems more apropos.

Discussion: https://postgr.es/m/16161.1518715186@sss.pgh.pa.us

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/51940f97607b7cb4d03bdd99e43abb1a1c6a0c47

Modified Files
--------------
src/backend/storage/lmgr/lwlock.c | 4 ++--
src/include/c.h                   | 8 ++++----
2 files changed, 6 insertions(+), 6 deletions(-)