improves ExecMakeFunctionResultNoSets

Attached patch improves ExecMakeFunctionResultNoSets, etc.

This patch uses InitFunctionCallInfoData macro instead of MemSet to
initialize FunctionCallInfoData.
An idea of this patch discussed in the "FunctionCallN improvement" thread.
(http://archives.postgresql.org/pgsql-hackers/2005-01/msg01054.php)
To achieve this, InitFunctionCallInfoData macro was moved from fmgr.c to
fmgr.h.

test sql:
select substr(c.relname, 1, 10) from pg_class c, pg_am, pg_amop;
(There are pg_am and pg_amop only to increase the number of the records.)

result of original code:
-----------------------------------------------------------------------
Each sample counts as 0.01 seconds.
% cumulative self self total
time seconds seconds calls s/call s/call name
21.43 0.36 0.36 219911 0.00 0.00
ExecMakeFunctionResultNoSets
7.14 0.48 0.12 219912 0.00 0.00 pg_mbstrlen_with_len
6.25 0.58 0.10 1102916 0.00 0.00 AllocSetAlloc
5.36 0.68 0.09 5936448 0.00 0.00 pg_euc_mblen
5.36 0.77 0.09 5936448 0.00 0.00 pg_mblen

result of after patch:
-----------------------------------------------------------------------
Each sample counts as 0.01 seconds.
% cumulative self self total
time seconds seconds calls s/call s/call name
7.52 0.10 0.10 5936448 0.00 0.00 pg_mblen
7.14 0.20 0.10 1104587 0.00 0.00 AllocSetAlloc
6.77 0.28 0.09 219912 0.00 0.00 text_substring
6.39 0.37 0.09 1547723 0.00 0.00 AllocSetFreeIndex
6.02 0.45 0.08 219912 0.00 0.00 pg_mbstrlen_with_len
4.51 0.51 0.06 5936448 0.00 0.00 pg_euc_mblen
4.51 0.57 0.06 442745 0.00 0.00 ExecProcNode
4.51 0.63 0.06 219911 0.00 0.00
ExecMakeFunctionResultNoSets

regards,

--- Atsushi Ogawa