Make sure HB_BEGIN_DECLS / HB_END_DECLS is only used in public headers

So we can use them to switch default visibility to internal if desired,
and use these to make only declared symbols public.

src/check-c-linkage-decls.sh

@@ -7,12 +7,20 @@ test -z "$srcdir" && srcdir=.
 stat=0
 
 test "x$HBHEADERS" = x && HBHEADERS=`find . -maxdepth 1 -name 'hb*.h'`
+test "x$HBSOURCES" = x && HBSOURCES=`find . -maxdepth 1 -name 'hb*.h'`
 
 
 for x in $HBHEADERS; do
 	test -f $srcdir/$x && x=$srcdir/$x
 	if ! grep -q HB_BEGIN_DECLS "$x" || ! grep -q HB_END_DECLS "$x"; then
-		echo "Ouch, file $x does not HB_BEGIN_DECLS / HB_END_DECLS"
+		echo "Ouch, file $x does not have HB_BEGIN_DECLS / HB_END_DECLS, but it should"
+		stat=1
+	fi
+done
+for x in $HBSOURCES; do
+	test -f $srcdir/$x && x=$srcdir/$x
+	if grep -q HB_BEGIN_DECLS "$x" || grep -q HB_END_DECLS "$x"; then
+		echo "Ouch, file $x has HB_BEGIN_DECLS / HB_END_DECLS, but it shouldn't"
 		stat=1
 	fi
 done

src/hb-fallback-shape-private.hh

@@ -32,16 +32,10 @@
 #include "hb-shape.h"
 
 
-HB_BEGIN_DECLS
-
-
 HB_INTERNAL hb_bool_t
 _hb_fallback_shape (hb_font_t          *font,
 		    hb_buffer_t        *buffer,
 		    const hb_feature_t *features,
 		    unsigned int        num_features);
 
-
-HB_END_DECLS
-
 #endif /* HB_FALLBACK_SHAPE_PRIVATE_HH */

src/hb-ot-shape-complex-indic-machine.rl

@@ -29,8 +29,6 @@
 
 #include "hb-private.hh"
 
-HB_BEGIN_DECLS
-
 %%{
   machine indic_syllable_machine;
   alphtype unsigned char;
@@ -110,6 +108,4 @@ find_syllables (const hb_ot_map_t *map, hb_buffer_t *buffer, hb_mask_t *mask_arr
   }%%
 }
 
-HB_END_DECLS
-
 #endif /* HB_OT_SHAPE_COMPLEX_INDIC_MACHINE_HH */