[...]
make[1]: Entering directory `/home/abs/base/bash/src/bash-2.05b/lib/malloc'
gcc -I. -I../.. -I../.. -I../../include -I../../lib -DHAVE_CONFIG_H -DSHELL
-march=i586 -O2 -pipe -DRCHECK -Dbotch=programming_error -c malloc.c
malloc.c:239: warning: integer constant is too large for "unsigned long" type
malloc.c: In function `internal_free':
malloc.c:904: error: label at end of compound statement
make[1]: *** [malloc.o] Error 1
make[1]: Leaving directory `/home/abs/base/bash/src/bash-2.05b/lib/malloc'
make: *** [lib/malloc/libmalloc.a] Error 1
==> ERROR: Build Failed. Aborting...
[...]

This error is the result of removing a deprecated extension in 3.4.0, a little more info can be found here:
http://mail.gnu.org/archive/html/bug-bash/2004-04/msg00290.html

Since a patchfile is already used to patch up various other pieces in the source, I took the liberty and integrated the necessary patch (just an added "return") into the already existant bash-2.05b.patch file. The new patch file has the md5sum '283204f05a9d724f4797811c3bac7838' and builds bash successfully.