SO issue: src/tutorial of 8.3.x fails to compile on Cygwin

Hi all

There's a new SO issue I thought might be worth a look, where someone's
unable to compile src/tutorial of 8.3.x using Cygwin/gcc . They tried
8.3.1 and 8.3.21.

I find it hard to care about Cygwin, let alone Cygwin builds for an
obsolete version, but it's possible this may affect 9.1/9.2 as well. I
don't have a Cygwin build env to check with. I thought I'd raise it in
case someone here does care about Cygwin and wanted to check that
src/tutorial builds in current versions.

http://stackoverflow.com/questions/12907015/compiling-postgresql-8-3-1-src-tutorial-on-cygwin-undefined-reference-to-set#comment17485248_12907015

The reported errors are:

funcs.c:19:1: warning: 'Pg_magic_func' redeclared without dllimport
attribute: previous dllimport ignored
funcs.c: In function 'copytext':
funcs.c:74:2: warning: implicit declaration of function 'SET_VARSIZE'

... followed by a linker error

funcs.o:funcs.c:(.text+0xb6): undefined reference to `_SET_VARSIZE'

that's caused by the compiler's assumption tht SET_VARSIZE is a function
since the macro doesn't seem to have been included.

--
Craig Ringer