libtextstyle: be sure to have ostream_printf and hyperlink support

Older versions of libtextstyle do not support them, rule them out.

Reported by Lars Wendler
https://lists.gnu.org/r/bug-bison/2020-07/msg00030.html

and by Arnold Robbins
https://lists.gnu.org/r/bug-bison/2020-07/msg00041.html and
https://lists.gnu.org/mailman/private/gawk-devel/2020-July/003988.html

and by Nelson H. F. Beebe
https://lists.gnu.org/mailman/private/gawk-devel/2020-July/003993.html

With support from Bruno Haible in gnulib
https://lists.gnu.org/r/bug-gnulib/2020-08/msg00000.html
thread starting at
https://lists.gnu.org/r/bug-gnulib/2020-07/msg00148.html

* configure.ac: Require libtextstyle 0.20.5.
* gnulib: Update.

7 files changed, 20 insertions, 8 deletions

diff --git a/NEWS b/NEWS
index cf79ac1e..717ff8a9 100644
--- a/NEWS
+++ b/NEWS
@@ -4,7 +4,9 @@ GNU Bison NEWS
 
 ** Bug fixes
 
-  Fixed a crash when a token alias contains a NUL byte.
+  Crash when a token alias contains a NUL byte.
+
+  Portability issues with libtextstyle.
 
 ** Changes
 
diff --git a/README b/README
index 489caa70..794d49e4 100644
--- a/README
+++ b/README
@@ -42,9 +42,11 @@ installing it.  In that case, do not use `src/bison`: it would use the
 As an experimental feature, diagnostics are now colored, controlled by the
 `--color` and `--style` options.
 
-To use them, install the libtextstyle library before configuring Bison.  It
-is available from https://alpha.gnu.org/gnu/gettext/, for instance
-https://alpha.gnu.org/pub/gnu/gettext/libtextstyle-0.20.5.tar.gz.
+To use them, install the libtextstyle library, 0.20.5 or newer, before
+configuring Bison.  It is available from https://alpha.gnu.org/gnu/gettext/,
+for instance https://alpha.gnu.org/gnu/gettext/libtextstyle-0.20.5.tar.gz,
+or as part of Gettext 0.21 or newer, for instance
+https://ftp.gnu.org/gnu/gettext/gettext-0.21.tar.gz.
 
 The option --color supports the following arguments:
 - always, yes: Enable colors.
@@ -61,6 +63,13 @@ To customize the styles, create a CSS file, say `bison-bw.css`, similar to
 then invoke bison with `--style=bison-bw.css`, or set the `BISON_STYLE`
 environment variable to `bison-bw.css`.
 
+In some diagnostics, bison uses libtextstyle to emit special escapes to
+generate clickable hyperlinks.  The environment variable
+`NO_TERM_HYPERLINKS` can be used to suppress them.  This may be useful for
+terminal emulators which produce garbage output when they receive the escape
+sequence for a hyperlink. Currently (as of 2020), this affects some versions
+of emacs, guake, konsole, lxterminal, rxvt, yakuake.
+
 ## Relocatability
 If you pass `--enable-relocatable` to `configure`, Bison is relocatable.
 
diff --git a/THANKS b/THANKS
index 5c64da3c..a97f2b03 100644
--- a/THANKS
+++ b/THANKS
@@ -106,6 +106,7 @@ Keith Browne              kbrowne@legato.com
 Ken Moffat                zarniwhoop@ntlworld.com
 Kiyoshi Kanazawa          yoi_no_myoujou@yahoo.co.jp
 Lars Maier                lars.maier@tefax.net
+Lars Wendler              polynomial-c@gentoo.org
 László Várady             laszlo.varady93@gmail.com
 Laurent Mascherpa         laurent.mascherpa@epita.fr
 Lie Yan                   lie.yan@kaust.edu.sa
diff --git a/configure.ac b/configure.ac
index c5750a6d..4993a2c6 100644
--- a/configure.ac
+++ b/configure.ac
@@ -60,6 +60,9 @@ AC_PROG_CXX
 # Gnulib (early checks).
 gl_EARLY
 
+# We want ostream_printf and hyperlink support.
+gl_LIBTEXTSTYLE_OPTIONAL([0.20.5])
+
 # Gnulib uses '#pragma GCC diagnostic push' to silence some
 # warnings, but older gcc doesn't support this.
 AC_CACHE_CHECK([whether pragma GCC diagnostic push works],
diff --git a/gnulib b/gnulib
-Subproject ac34618e85013bfec4650f02e8e79c5de6d80fb
+Subproject 37b6f1294620be849f951dcb2f505207b435f88
diff --git a/lib/.gitignore b/lib/.gitignore
index 7f9045d4..758edcc0 100644
--- a/lib/.gitignore
+++ b/lib/.gitignore
@@ -192,8 +192,6 @@
 /localcharset.h
 /locale.h
 /locale.in.h
-/localtime-buffer.c
-/localtime-buffer.h
 /lstat.c
 /malloc.c
 /malloca.c
diff --git a/m4/.gitignore b/m4/.gitignore
index cca78f48..9bc07270 100644
--- a/m4/.gitignore
+++ b/m4/.gitignore
@@ -67,7 +67,6 @@
 /intlmacosx.m4
 /intmax.m4
 /intmax_t.m4
-/inttypes-pri.m4
 /inttypes.m4
 /inttypes_h.m4
 /isnan.m4
@@ -97,7 +96,6 @@
 /locale-ja.m4
 /locale-zh.m4
 /locale_h.m4
-/localtime-buffer.m4
 /lock.m4
 /longlong.m4
 /lstat.m4
@@ -117,6 +115,7 @@
 /msvc-inval.m4
 /msvc-nothrow.m4
 /multiarch.m4
+/musl.m4
 /nls.m4
 /nocrash.m4
 /non-recursive-gnulib-prefix-hack.m4