[Exim] Problem building exim-4.22 with sa-exim

I am trying to build the above. I think I have folowed the instructions
right ie:

copy sa-exim-3.1/sa-exim.c to exim-4.22/src/local_scan.c
make sa-exim.h in sa-exim-3.1
copy sa-exim-3.1/sa-exim.h to exim-4.22/src/sa-exim.h

edit Makefile as normal

type make

this is what I get

make[2]: Leaving directory `/root/exim-4.22/build-Linux-i386/pcre'
gcc -c -O2 -I/usr/include  -DCOMPILE_UTILITY -o util-spool_in.o
spool_in.c
In file included from exim.h:354,
                 from spool_in.c:12:
dbstuff.h:550: parse error before "BOOL"
dbstuff.h:550: warning: no semicolon at end of struct or union
dbstuff.h:553: parse error before "text"
dbstuff.h:553: warning: data definition has no type or storage class
dbstuff.h:554: parse error before '}' token
dbstuff.h:554: warning: data definition has no type or storage class
dbstuff.h:610: parse error before "uschar"
dbstuff.h:610: warning: no semicolon at end of struct or union
dbstuff.h:611: warning: data definition has no type or storage class
In file included from exim.h:355,
                 from spool_in.c:12:
structs.h:32: parse error before "BOOL"
structs.h:32: warning: no semicolon at end of struct or union
structs.h:33: warning: data definition has no type or storage class
"errlog" 1622L, 92297C
1,1           Top

and it continues with similar output

stock source compiles fine

This is on Red Hat 9