Fix defalt_makefiles[] for MS-Windows.

* read.c (read_all_makefiles) [WINDOWS32]: Remove the redundant
"makefile" and add "makefile.mak".

Copyright-paperwork-exempt: yes
[SV 42695] Fix compilation error on MS-Windows.

* main.c [WINDOWS32]: Don't declare 'program' as 'const char *',
since it is modified in 'main'.