patch 8.1.0914: code related to findfile() is spread out

Problem:    Code related to findfile() is spread out.
Solution:   Put findfile() related code into a new source file. (Yegappan
            Lakshmanan, closes #3934)
diff --git a/src/README.txt b/src/README.txt
index e1dc36f..52edeb7 100644
--- a/src/README.txt
+++ b/src/README.txt
@@ -22,8 +22,10 @@
 	diff.c		diff mode (vimdiff)
 	eval.c		expression evaluation
 	fileio.c	reading and writing files
+	findfile.c	search for files in 'path'
 	fold.c		folding
 	getchar.c	getting characters and key mapping
+	indent.c	C and Lisp indentation
 	mark.c		marks
 	mbyte.c		multi-byte character handling
 	memfile.c	storing lines for buffers in a swapfile