Merge with gnulib, pacifying GCC 7

This incorporates:
2017-05-16 manywarnings: update for GCC 7
2017-05-15 sys_select: Avoid "was expanded before it was required"
* configure.ac (nw): Suppress GCC 7’s new -Wduplicated-branches and
-Wformat-overflow=2 options, due to too many false alarms.
* doc/misc/texinfo.tex, lib/strftime.c, m4/manywarnings.m4:
Copy from gnulib.
* m4/gnulib-comp.m4: Regenerate.
* src/coding.c (decode_coding_iso_2022):
Fix bug uncovered by -Wimplicit-fallthrough.
* src/conf_post.h (FALLTHROUGH): New macro.
Use it to mark all switch cases that fall through.
* src/editfns.c (styled_format): Use !, not ~, on bool.
* src/gtkutil.c (xg_check_special_colors):
When using sprintf, don’t trust Gtk to output colors in [0, 1] range.
(xg_update_scrollbar_pos): Avoid use of possibly-uninitialized bool;
this bug was actually caught by Clang.
* src/search.c (boyer_moore):
Tell GCC that CHAR_BASE, if nonzero, must be a non-ASCII character.
* src/xterm.c (x_draw_glyphless_glyph_string_foreground):
Tell GCC that glyph->u.glyphless.ch must be a character.

1 files changed, 8 insertions, 2 deletions

diff --git a/doc/misc/texinfo.tex b/doc/misc/texinfo.tex
index 9cd73101c1f..8204f3e3aeb 100644
--- a/doc/misc/texinfo.tex
+++ b/doc/misc/texinfo.tex
@@ -3,7 +3,7 @@
 % Load plain if necessary, i.e., if running under initex.
 \expandafter\ifx\csname fmtname\endcsname\relax\input plain\fi
 %
-\def\texinfoversion{2017-04-14.11}
+\def\texinfoversion{2017-05-14.14}
 %
 % Copyright 1985, 1986, 1988, 1990, 1991, 1992, 1993, 1994, 1995,
 % 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006,
@@ -9118,7 +9118,13 @@ end
     \xdef\safexrefname{#1}%
   }%
   %
-  \expandafter\gdef\csname XR\safexrefname\endcsname{#2}% remember this xref
+  \bgroup
+    \expandafter\gdef\csname XR\safexrefname\endcsname{#2}%
+  \egroup
+  % We put the \gdef inside a group to avoid the definitions building up on 
+  % TeX's save stack, which can cause it to run out of space for aux files with 
+  % thousands of lines.  \gdef doesn't use the save stack, but \csname does
+  % when it defines an unknown control sequence as \relax. 
   %
   % Was that xref control sequence that we just defined for a float?
   \expandafter\iffloat\csname XR\safexrefname\endcsname