pgsql: jit: Reference function pointer types via llvmjit_types.c.

jit: Reference function pointer types via llvmjit_types.c.

It is error prone (see 5da871bfa1b) and verbose to manually create function
types. Add a helper that can reference a function pointer type via
llvmjit_types.c and and convert existing instances of manual creation.

Author: Andres Freund <andres@anarazel.de>
Reviewed-By: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/20201207212142.wz5tnbk2jsaqzogb@alap3.anarazel.de

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/df99ddc70b971a991c5111a33f2f08bd7945d5c2

Modified Files
--------------
src/backend/jit/llvm/llvmjit.c       | 95 ++++++++++++++++++++++--------------
src/backend/jit/llvm/llvmjit_expr.c  | 33 +++----------
src/backend/jit/llvm/llvmjit_types.c |  2 +
src/include/jit/llvmjit.h            |  2 +
4 files changed, 69 insertions(+), 63 deletions(-)