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, 12 deletions

diff --git a/src/eval.c b/src/eval.c
index 848955c2794..98d25cc4fed 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -3212,7 +3212,7 @@ do_specbind (struct Lisp_Symbol *sym, union specbinding *bind,
           set_default_internal (specpdl_symbol (bind), value, bindflag);
           return;
         }
-      /* FALLTHROUGH */
+      FALLTHROUGH;
     case SYMBOL_LOCALIZED:
       set_internal (specpdl_symbol (bind), value, Qnil, bindflag);
       break;
@@ -3390,12 +3390,10 @@ do_one_unbind (union specbinding *this_binding, bool unwinding,
                             Qnil, bindflag);
             break;
           }
-        else
-          { /* FALLTHROUGH!!
-               NOTE: we only ever come here if make_local_foo was used for
-               the first time on this var within this let.  */
-          }
       }
+      /* Come here only if make_local_foo was used for the first time
+         on this var within this let.  */
+      FALLTHROUGH;
     case SPECPDL_LET_DEFAULT:
       set_default_internal (specpdl_symbol (this_binding),
                             specpdl_old_value (this_binding),
@@ -3676,12 +3674,10 @@ backtrace_eval_unrewind (int distance)
                 SET_SYMBOL_VAL (XSYMBOL (sym), old_value);
                 break;
               }
-            else
-              { /* FALLTHROUGH!!
-                   NOTE: we only ever come here if make_local_foo was used for
-                   the first time on this var within this let.  */
-              }
           }
+          /* Come here only if make_local_foo was used for the first
+             time on this var within this let.  */
+          FALLTHROUGH;
         case SPECPDL_LET_DEFAULT:
           {
             Lisp_Object sym = specpdl_symbol (tmp);
@@ -3837,7 +3833,7 @@ mark_specpdl (union specbinding *first, union specbinding *ptr)
         case SPECPDL_LET_DEFAULT:
         case SPECPDL_LET_LOCAL:
           mark_object (specpdl_where (pdl));
-          /* Fall through.  */
+          FALLTHROUGH;
         case SPECPDL_LET:
           mark_object (specpdl_symbol (pdl));
           mark_object (specpdl_old_value (pdl));