Problematic gmpn_popcount()

[Gisle Vanem]

I'm still struggling in building and getting GMP + MPFR to run okay
on MingW. (ref. the 'Announce: MPFR 2.3.1 is released' thread).

In this process I discovered it is plain impossible to build GMP 4.2.2 as 
a DLL and at the same time use the .asm files in GMP. I had to use
the 'generic' functions/files. It seems -DDLL_EXPORT (mpn/asm-defs.m4) 
has no effect. I've managed to replace all .asm function, except for this one:

MingW_obj/get_str.o: In function `mpfr_get_str':
G:/MingW32/src/gnu/mpfr/get_str.c:1651: undefined reference to `_imp____gmpn_popcount'
MingW_obj/strtofr.o: In function `parsed_string_to_mpfr':
G:/MingW32/src/gnu/mpfr/strtofr.c:641: undefined reference to `_imp____gmpn_popcount'

Seems there is no mpn/generic/popcount.c. How do I get past this hurdle?

--gv