implement the nonstandard GNU function fpurge
this is a really ugly and backwards function, but its presence will
prevent lots of broken gnulib software from trying to define its own
version of fpurge and thereby failing to build or worse.
diff --git a/include/stdio.h b/include/stdio.h
index 69178cc..b54fe19 100644
--- a/include/stdio.h
+++ b/include/stdio.h
@@ -158,6 +158,7 @@
int vasprintf(char **, const char *, va_list);
void setlinebuf(FILE *);
void setbuffer(FILE *, char *, size_t);
+int fpurge(FILE *);
#endif
#ifdef __cplusplus