buildworld failure 4.9 Stable --> 5.2 Release

[Goodleaf, John M]

Hello,

I'm trying to upgrade a system from 4.9 (Stable) to 5.2 release. I get a
buildworld failure with aand error that reads like this:

In file included from /usr/src/lib/libkvm/kvm.c:62:
/usr/src/lib/libkvm/kvm.h:41:24: sys/_types.h: No such file or directory
In file included from /usr/src/lib/libkvm/kvm.c:62:
/usr/src/lib/libkvm/kvm.h:49: error: syntax error before "size_t"
/usr/src/lib/libkvm/kvm.h:49: warning: useless keyword or type name in empty
declaration
/usr/src/lib/libkvm/kvm.h:49: warning: empty declaration
/usr/src/lib/libkvm/kvm.h:54: error: syntax error before "ssize_t"
/usr/src/lib/libkvm/kvm.h:54: warning: useless keyword or type name in empty
declaration
/usr/src/lib/libkvm/kvm.h:54: warning: empty declaration

Any ideas how to fix this?

Thanks,
John

PS My make.conf file looks like this:

MODULES_WITH_WORLD=true
USA_RESIDENT=YES
CFLAGS= -O -pipe
NOGAMES=        true
NOINFO= true
NOFORTRAN=      true
NO_LPR=         true
KERNCONF=CLYDE
NO_SENDMAIL=    true
COPTFLAGS= -O -pipe
CPUTYPE=        pentium4
CXXFLAGS+= -fmemoize-lookups -fsave-memoized
PERL_VER=5.8.1
PERL_VERSION=5.8.1
PERL_ARCH=mach
NOPERL=yo
NO_PERL=yo
NO_PERL_WRAPPER=yo