Here are some files form other packages that I have changed.

specs (/usr/lib/gcc-lib/i486-linux/2.4.5/specs)
The changes allow you to use the '-checker' option. If you have the original
specs, you can copy it.

tc-i386.h & tc-i386.c (gas-2.1.1/gas/config/tc-i386.?)
These file implements code insertion. Copy them, if you have gas sources.

i386.h (gas-2.1.1/gas/include/opcodes/i386.h)
code insertion(2). I have added one filed in the template structure. So, if
you use this file with another package (e.g. gdb), see tc-i386.h

Makeconfig/Makefile (libc-linux/)
allow to build libc with make CHECKER=true

libc-changes.taz
untar it in libc-linux/sysdeps. It is necessary if you want to compile a
checkered c-lib.