Minor, fix warnings raised when built with -std=c++2a

Follow up to c184180,

It was raising,

  src/hb-ot-layout-common.hh:1067:63: warning: implicit capture of 'this' with a capture default of '=' is deprecated [-Wdeprecated-this-capture]
      | hb_filter ([=] (const OffsetTo<TSubTable> &_) { return (this+_).intersects (glyphset, lookup_type); })
                                                                ^
  src/hb-ot-layout-common.hh:1067:19: note: add an explicit capture of 'this' to capture '*this' by reference
      | hb_filter ([=] (const OffsetTo<TSubTable> &_) { return (this+_).intersects (glyphset, lookup_type); })
                    ^
                     , this

and

  src/hb-ot-layout-common.hh:2626:38: warning: implicit capture of 'this' with a capture default of '=' is deprecated [-Wdeprecated-this-capture]
                  { r.collect_lookups (this, lookup_indexes); })
                                       ^
  src/hb-ot-layout-common.hh:2625:18: note: add an explicit capture of 'this' to capture '*this' by reference
      | hb_apply ([=] (const FeatureTableSubstitutionRecord& r)
                   ^
                    , this

and

  src/hb-ot-hdmx-table.hh:141:44: error: implicit capture of 'this' with a capture default of '=' is deprecated [-Werror,-Wdeprecated-this-capture]
                          return device_record->widthsZ.as_array (get_num_glyphs ()) [_];
                                                                  ^
  src/hb-ot-hdmx-table.hh:137:17: note: add an explicit capture of 'this' to capture '*this' by reference
              | hb_map ([=] (hb_codepoint_t _)
                         ^
                          , this

.circleci/config.yml

@@ -111,7 +111,9 @@ jobs:
       - run: LD_LIBRARY_PATH="$PWD/freetype-2.9/objs/.libs" make check || .ci/fail.sh
       - run: make clean
       - run: make -Csrc CPPFLAGS="-DHB_TINY -DHB_NO_OT_FONT" libharfbuzz-subset.la && make clean
-      - run: clang -c src/hb-*.cc -DHB_NO_MT
+      - run: clang -c src/harfbuzz.cc -DHB_NO_MT
+      # -Werror -Werror=deprecated-this-capture can be added but it will confuse contributors so let's skip for now
+      - run: clang -c src/hb-*.cc -DHB_NO_MT -std=c++2a -fno-exceptions
 
   gcc-valgrind:
     docker:

src/hb-ot-hdmx-table.hh

@@ -134,10 +134,10 @@ struct hdmx
 	  auto row =
 	    + hb_range (c->plan->num_output_glyphs ())
 	    | hb_map (c->plan->reverse_glyph_map)
-	    | hb_map ([=] (hb_codepoint_t _)
+	    | hb_map ([this, c, device_record] (hb_codepoint_t _)
 		      {
 			if (c->plan->is_empty_glyph (_))
-			  return Null(HBUINT8);
+			  return Null (HBUINT8);
 			return device_record->widthsZ.as_array (get_num_glyphs ()) [_];
 		      })
 	    ;

src/hb-ot-layout-common.hh

@@ -1064,7 +1064,7 @@ struct Lookup
     const hb_set_t *glyphset = c->plan->glyphset ();
     unsigned int lookup_type = get_type ();
     + hb_iter (get_subtables <TSubTable> ())
-    | hb_filter ([=] (const OffsetTo<TSubTable> &_) { return (this+_).intersects (glyphset, lookup_type); })
+    | hb_filter ([this, glyphset, lookup_type] (const OffsetTo<TSubTable> &_) { return (this+_).intersects (glyphset, lookup_type); })
     | hb_apply (subset_offset_array (c, out->get_subtables<TSubTable> (), this, out, lookup_type))
     ;
 
@@ -2622,10 +2622,8 @@ struct FeatureTableSubstitution
   {
     + hb_iter (substitutions)
     | hb_filter (feature_indexes, &FeatureTableSubstitutionRecord::featureIndex)
-    | hb_apply ([=] (const FeatureTableSubstitutionRecord& r)
+    | hb_apply ([this, lookup_indexes] (const FeatureTableSubstitutionRecord& r)
-                {
+		{ r.collect_lookups (this, lookup_indexes); })
-                  r.collect_lookups (this, lookup_indexes);
-                })
     ;
   }