build: enable -Wmismatched-dealloc

[Akim Demaille]

commit 272da17cfdd4fd6e3b99e27d777208fb67493d57
Author: Akim Demaille <akim.demaille@gmail.com>
Date:   Sun Aug 8 08:36:49 2021 +0200

    gnulib: update

diff --git a/gnulib b/gnulib
index 6dae7213..6ccfbd64 160000
--- a/gnulib
+++ b/gnulib
@@ -1 +1 @@
-Subproject commit 6dae7213a2e67c0da56f9bb110e2500df4edeeaa
+Subproject commit 6ccfbd6495f2849b1aeea84f73327f6ced0080a7





commit dabde7c560f249f30e47a1fce7cf29891023f3fc
Author: Akim Demaille <akim.demaille@gmail.com>
Date:   Sun Aug 8 08:49:32 2021 +0200

    build: enable -Wmismatched-dealloc
    
    * configure.ac (warn_common): Here.

diff --git a/configure.ac b/configure.ac
index f7d6035c..f4e02dd6 100644
--- a/configure.ac
+++ b/configure.ac
@@ -133,7 +133,7 @@ if test "$enable_gcc_warnings" = yes; then
   warn_common='-Wall -Wextra
     -Wcast-align -Wchar-subscripts
     -fparse-all-comments -Wdocumentation
-    -Wformat -Wimplicit-fallthrough -Wnull-dereference
+    -Wformat -Wimplicit-fallthrough -Wmismatched-dealloc -Wnull-dereference
     -Wno-sign-compare -Wno-tautological-constant-out-of-range-compare
     -Wpointer-arith -Wshadow -Wstrict-aliasing
     -Wwrite-strings