varint - varint: refactor operations on VarInts to functions with normal

Log Message:
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refactor operations on VarInts to functions with normal C apis, to make them easier to call from other VarInt operations (avoiding DirectFunctionCallX). Add modulus and divmod functions.

Modified Files:
--------------
varint:
Makefile (r1.2 -> r1.3)
(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/varint/varint/Makefile.diff?r1=1.2&r2=1.3)
uninstall_varint.sql (r1.1 -> r1.2)
(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/varint/varint/uninstall_varint.sql.diff?r1=1.1&r2=1.2)
varint.c (r1.4 -> r1.5)
(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/varint/varint/varint.c.diff?r1=1.4&r2=1.5)
varint.h (r1.4 -> r1.5)
(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/varint/varint/varint.h.diff?r1=1.4&r2=1.5)
varint.sql.in (r1.4 -> r1.5)
(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/varint/varint/varint.sql.in.diff?r1=1.4&r2=1.5)
varint/expected:
division.out (r1.1 -> r1.2)
(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/varint/varint/expected/division.out.diff?r1=1.1&r2=1.2)
multiplication.out (r1.1 -> r1.2)
(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/varint/varint/expected/multiplication.out.diff?r1=1.1&r2=1.2)
subtraction.out (r1.1 -> r1.2)
(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/varint/varint/expected/subtraction.out.diff?r1=1.1&r2=1.2)
varint/sql:
division.sql (r1.1 -> r1.2)
(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/varint/varint/sql/division.sql.diff?r1=1.1&r2=1.2)
subtraction.sql (r1.1 -> r1.2)
(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/varint/varint/sql/subtraction.sql.diff?r1=1.1&r2=1.2)

Added Files:
-----------
varint:
varint_core.c (r1.1)
(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/varint/varint/varint_core.c?rev=1.1&content-type=text/x-cvsweb-markup)
varint_core.h (r1.1)
(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/varint/varint/varint_core.h?rev=1.1&content-type=text/x-cvsweb-markup)