pgsql: Add special case fast-paths for strict functions

Add special case fast-paths for strict functions

Many STRICT function calls will have one or two arguments, in which
case we can speed up checking for NULL input by avoiding setting up
a loop over the arguments. This adds EEOP_FUNCEXPR_STRICT_1 and the
corresponding EEOP_FUNCEXPR_STRICT_2 for functions with one and two
arguments respectively.

Author: Andres Freund <andres(at)anarazel(dot)de>
Co-authored-by: Daniel Gustafsson <daniel(at)yesql(dot)se>
Reviewed-by: Andreas Karlsson <andreas(at)proxel(dot)se>
Discussion: https://postgr.es/m/415721CE-7D2E-4B74-B5D9-1950083BA03E@yesql.se
Discussion: https://postgr.es/m/20191023163849.sosqbfs5yenocez3@alap3.anarazel.de

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/d35d32d7112bc632c6a305e9dffdec0082bbdf00

Modified Files
--------------
src/backend/executor/execExpr.c | 13 +++++-
src/backend/executor/execExprInterp.c | 74 ++++++++++++++++++++++++++++++++++-
src/backend/jit/llvm/llvmjit_expr.c | 7 +++-
src/include/executor/execExpr.h | 7 +++-
4 files changed, 96 insertions(+), 5 deletions(-)