Revert removal of unreadCh change for performance

Turns out unreadCh is much more efficient than seek(-1, SEEK_CUR).
Update comments and code to reflect this.

1 files changed, 0 insertions, 9 deletions

diff --git a/ChangeLog b/ChangeLog
index a173ff00..edc4ecce 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -81,15 +81,6 @@
 	disables passing -rpath to the linker when building shared
 	libraries with libtool. Fixes #422.
 
-2020-10-18  Jay Berkenbilt  <ejb@ql.org>
-
-	* Note that InputSource::unreadCh is deprecated and will be
-	removed in qpdf 11. Use seek(-1, SEEK_CUR) instead. This is what
-	it has always effectively done with some input sources and some
-	operating systems which don't allow unreading other than the most
-	recently read character. InputSource::unreadCh is no longer used
-	internally within libqpdf.
-
 2020-10-16  Jay Berkenbilt  <ejb@ql.org>
 
 	* Accept pull request that improves how the Windows native crypto