patch 8.0.0817: cannot get the terminal line at the cursor

Problem:    Cannot get the line of a terminal window at the cursor.
Solution:   Make the row argunt optionsl. (Yasuhiro Matsumoto, closes #1898)
diff --git a/runtime/doc/eval.txt b/runtime/doc/eval.txt
index 9d26f36..dee7b64 100644
--- a/runtime/doc/eval.txt
+++ b/runtime/doc/eval.txt
@@ -1,4 +1,4 @@
-*eval.txt*	For Vim version 8.0.  Last change: 2017 Jul 29
+*eval.txt*	For Vim version 8.0.  Last change: 2017 Jul 30
 
 
 		  VIM REFERENCE MANUAL	  by Bram Moolenaar
@@ -2371,10 +2371,10 @@
 tempname()			String	name for a temporary file
 term_getattr({attr}, {what}	Number	get the value of attribute {what}
 term_getjob({buf})		Job	get the job associated with a terminal
-term_getline({buf}, {row})	String	get a line of text from a terminal
+term_getline({buf}[, {row}])	String	get a line of text from a terminal
 term_getsize({buf})		List	get the size of a terminal
 term_list()			List	get the list of terminal buffers
-term_scrape({buf}, {row})	List	get row of a terminal screen
+term_scrape({buf}[, {row}])	List	get row of a terminal screen
 term_sendkeys({buf}, {keys})	none	send keystrokes to a terminal
 term_start({cmd}, {options})	Job	open a terminal window and run a job
 term_wait({buf})		Number  wait for screen to be updated
@@ -7914,12 +7914,13 @@
 		Get the Job associated with terminal window {buf}.
 		{buf} is used as with |term_getsize()|.
 
-term_getline({buf}, {row})				*term_getline()*
+term_getline({buf} [, {row}])				*term_getline()*
 		Get a line of text from the terminal window of {buf}.
 		{buf} is used as with |term_getsize()|.
 
 		The first line has {row} zero.  When {row} is invalid an empty
-		string is returned.
+		string is returned. When {row} is omitted, the cursor line is
+		used.
 
 term_getsize({buf})					*term_getsize()*
 		Get the size of terminal {buf}. Returns a list with two
@@ -7930,17 +7931,17 @@
 		buffer does not exist or is not a terminal window, an empty
 		list is returned.
 
-term_list(})						*term_list()*
+term_list()						*term_list()*
 		Return a list with the buffer numbers of all buffers for
 		terminal windows.
 
-term_scrape({buf}, {row})				*term_scrape()*
+term_scrape({buf} [, {row}])				*term_scrape()*
 		Get the contents of {row} of terminal screen of {buf}.
 		For {buf} see |term_getsize()|.
 
 		The first {row} is zero.  When {row} is invalid an empty list
-		is returned.
-		
+		is returned. When {row} is omitted the cursor line is used.
+
 		Return a List containing a Dict for each screen cell: 
 		    "chars"	character(s) at the cell
 		    "fg"	foreground color as #rrggbb