5.1 build failure on OS X

When I try to build 5.1 on my OS X 10.2.8 box I get this:

gcc -I../../include -I../../include -I. -I../.. -I.
-I./../.. -I./../../snmplib -I./.. -I.. -g -O2
-Ddarwin6 -c ucd-snmp/disk.c -fno-common -DPIC -o
ucd-snmp/disk.lo
ucd-snmp/disk.c: In function `find_device':
ucd-snmp/disk.c:529: error: parse error before "else"
ucd-snmp/disk.c: At top level:
ucd-snmp/disk.c:541: error: parse error before "return"
make[2]: *** [ucd-snmp/disk.lo] Error 1
make[1]: *** [subdirs] Error 1
make: *** [subdirs] Error 1

also I noticed in the configure output, althought I
don't know if it's related or anything to be concerned
about:

checking net/route.h presence... yes
configure: WARNING: net/route.h: present but cannot be
compiled
configure: WARNING: net/route.h: check for missing
prerequisite headers?
configure: WARNING: net/route.h: proceeding with the
preprocessor's result
configure: WARNING: ##
------------------------------------ ##
configure: WARNING: ## Report this to
bug-autoconf@gnu.org. ##
configure: WARNING: ##
------------------------------------ ##

for this and a fair number of other system headers.