MinGW needs an extra symbol _WIN32_IE defined to a particular value before

it'll let you see an identifier (SHGFP_TYPE_CURRENT) referenced since r7082.
(Actually, you need a pretty recent w32api before it's there at all.)

Morally, this should be defined for all toolchains, not just MinGW/Cygwin, but  I'll leave that to people who have those toolchains.
<http://msdn2.microsoft.com/en-us/library/aa383745.aspx>

Also add some other comments on our use of this API (since it's a horrible one
that I suspect will come back and haunt us...)

[originally from svn r7087]
[r7082 == dbbd6eb5ec]
[this svn revision also touched putty-wishlist]

Recipe

@@ -218,6 +218,13 @@ install-strip:
 CFLAGS += -DMACOSX
 !end
 
+# Random symbols.
+!begin cygwin vars
+# _WIN32_IE is required to expose identifiers that only make sense on
+# systems with IE5+ installed, such as some arguments to SHGetFolderPath().
+CFLAGS += -D_WIN32_IE=0x0500
+!end
+
 # ------------------------------------------------------------
 # Definitions of object groups. A group name, followed by an =,
 # followed by any number of objects or other already-defined group