patch 8.1.1908: every popup window consumes a buffer number
Problem: Every popup window consumes a buffer number.
Solution: Recycle buffers only used for popup windows. Do not list popup
window buffers.
diff --git a/src/proto/buffer.pro b/src/proto/buffer.pro
index 0378b15..052536e 100644
--- a/src/proto/buffer.pro
+++ b/src/proto/buffer.pro
@@ -1,4 +1,5 @@
/* buffer.c */
+int get_highest_fnum(void);
void buffer_ensure_loaded(buf_T *buf);
int open_buffer(int read_stdin, exarg_T *eap, int flags);
void set_bufref(bufref_T *bufref, buf_T *buf);