Compile failure with SSL

I think this is another on of those 'might be Win32 specific' problems.
When building on XP, with OpenSSL 0.9.7c (from the bitWalk MinGW tools),
I get the following failure:

gcc -O2 -fno-strict-aliasing -Wall -Wmissing-prototypes
-Wmissing-declarations -I../../../src/include -I./src/include/port/win32
-DEXEC_BACKEND "-I../../../src/include/port/win32" -DBUILDING_DLL -c
-o be-secure.o be-secure.c
be-secure.c: In function `initialize_SSL':
be-secure.c:653: `S_IRWXG' undeclared (first use in this function)
be-secure.c:653: (Each undeclared identifier is reported only once
be-secure.c:653: for each function it appears in.)
be-secure.c:653: `S_IRWXO' undeclared (first use in this function)
be-secure.c:654: warning: implicit declaration of function `getuid'
make[3]: *** [be-secure.o] Error 1
make[3]: Leaving directory `/cvs/pgsql/src/backend/libpq'

I have run 'make distclean' and './configure --with-openssl' to make
sure everything is consistent.

Any ideas?

Regards, Dave