Update runtime files.
diff --git a/runtime/doc/options.txt b/runtime/doc/options.txt
index 927931c..c6fc424 100644
--- a/runtime/doc/options.txt
+++ b/runtime/doc/options.txt
@@ -1,4 +1,4 @@
-*options.txt* For Vim version 8.0. Last change: 2017 Mar 22
+*options.txt* For Vim version 8.0. Last change: 2017 May 08
VIM REFERENCE MANUAL by Bram Moolenaar
@@ -862,6 +862,12 @@
< Vim will guess the value. In the GUI this should work correctly,
in other cases Vim might not be able to guess the right value.
+ When the t_BG option is set, Vim will use it to request the background
+ color from the terminal. If the returned RGB value is dark/light and
+ 'background' is not dark/light, 'background' will be set and the
+ screen is redrawn. This may have side effects, make t_BG empty in
+ your .vimrc if you suspect this problem.
+
When starting the GUI, the default value for 'background' will be
"light". When the value is not set in the .gvimrc, and Vim detects
that the background is actually quite dark, 'background' is set to
@@ -2700,7 +2706,7 @@
Makes the 'g' and 'c' flags of the ":substitute" command to be
toggled each time the flag is given. See |complex-change|. See
also 'gdefault' option.
- Switching this option on is discouraged!
+ Switching this option on may break plugins!
*'emoji'* *'emo'* *'noemoji'* *'noemo'*
'emoji' 'emo' boolean (default: on)