Bootstrapping trunk fails on windows due to errors in coding.c

[Eric Lilja]

Seems to be due to the recent changes in coding.c, here's a transcript 
from the relevant part of the bootstrap:
coding.c: In function `encode_coding_emacs_mule':
coding.c:2196: error: invalid lvalue in assignment
coding.c: In function `setup_iso_safe_charsets':
coding.c:2486: error: invalid lvalue in assignment
coding.c: In function `Fdefine_coding_system_internal':
coding.c:8693: error: invalid lvalue in assignment
coding.c:8698: error: invalid lvalue in assignment
coding.c:8702: error: invalid lvalue in assignment
coding.c:8745: error: invalid lvalue in assignment
coding.c:8751: error: invalid lvalue in assignment
coding.c:8753: error: invalid lvalue in assignment
coding.c:8758: error: invalid lvalue in assignment
coding.c:8763: error: invalid lvalue in assignment
coding.c:8767: error: invalid lvalue in assignment
coding.c:8771: error: invalid lvalue in assignment
coding.c:8775: error: invalid lvalue in assignment
coding.c:8779: error: invalid lvalue in assignment
coding.c:8783: error: invalid lvalue in assignment
coding.c:8787: error: invalid lvalue in assignment
coding.c:8812: error: invalid lvalue in assignment
coding.c:8910: error: invalid lvalue in assignment
coding.c:8964: error: invalid lvalue in assignment
coding.c:9024: error: invalid lvalue in assignment
coding.c:9030: error: invalid lvalue in assignment
coding.c:9047: error: invalid lvalue in assignment
coding.c:9085: error: invalid lvalue in assignment
coding.c:9099: error: invalid lvalue in assignment
coding.c:9104: error: invalid lvalue in assignment
coding.c:9112: error: invalid lvalue in assignment
coding.c:9115: error: invalid lvalue in assignment
coding.c:9119: error: invalid lvalue in assignment
coding.c: In function `Fcoding_system_put':
coding.c:9194: error: invalid lvalue in assignment
coding.c:9202: error: invalid lvalue in assignment
coding.c:9208: error: invalid lvalue in assignment
coding.c:9214: error: invalid lvalue in assignment
coding.c:9219: error: invalid lvalue in assignment
coding.c:9224: error: invalid lvalue in assignment
coding.c:9228: error: invalid lvalue in assignment
coding.c:9232: error: invalid lvalue in assignment

This was with --enable-font-backend, using cygwin's bash, latest 
mingw32-make, cygwin's gcc in mingw-mode on both winxp and vista (both 
32-bit).

- Eric