preproc: handle %+ even during early token replacement

preproc: handle %+ even during early token replacement

Preexisting code seems to rely on %+ being processed even during early
token replacement, e.g. Syslinux contains the following code:

%macro          superb 1
bx %+ %1        equ SuperInfo+($-superblock)*8+4
bs %+ %1        equ $
                zb 1
%endmacro

... which is expected to work when invoked as:

                superb Media

As a result, set handle_paste_tokens to true at all times; assuming
this turns out to be the way things are we can really just remove it
as an option.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>