MSVC C++ compatibility: Rename the internal name of union _GUID becau…

…se _GUID is a builtin keyword here.

This does not concern the typedef name, only the internal union name,
so it doesn't harm us.

git-svn-id: svn+ssh://svn.gnucash.org/repo/gnucash/trunk@18772 57a11ea4-9604-0410-9ed3-97b8803252fd

src/libqof/qof/guid.h

@@ -51,7 +51,7 @@
 
 /** The type used to store guids */
 #define GUID_DATA_SIZE	16
-typedef union _GUID
+typedef union GNC_INTERNAL_GUID
 {
     guchar data[GUID_DATA_SIZE];