Queued keys are not discarded when exiting F mode with ^X

[gwsw]

Steps to reproduce:

1. Run less file.
2. Type F.
3. While "Waiting for data" is displayed, type g then ^C.
4. Observe that the display remains as EOF as expected.
5. Type F.
6. While "Waiting for data" is displayed, type g then ^X.

Expected result:
Display should remain at EOF as it does when ^C is used.

Actual result:
Display jumps to beginning of file.

Tested on less-696.

[gwsw]

Fixed in 0b92e33.