doc: modify style for texi2html 1.78+

The generated HTML files are similar to the ones generated with
texi2html 1.56k used on the website.

Tested with texi2html 1.78 and 5.0. 1.78 is the minimal recommended
version.

The removed @sp from the titlepage section were ignored until
texi2html 5.0. If not removed the pages generated by 5.0 will have ugly
empty space around the title.
(cherry picked from commit a8f0814a74)

Makefile

@@ -123,8 +123,8 @@ doc/ffprobe.pod doc/ffprobe.html: doc/demuxers.texi doc/indevs.texi doc/protocol
 doc/libavfilter.html: doc/filters.texi
 
 doc/%.html: TAG = HTML
-doc/%.html: doc/%.texi
+doc/%.html: doc/%.texi $(SRC_PATH_BARE)/doc/t2h.init
-	$(M)cd doc && texi2html -monolithic -number $(<:doc/%=%)
+	$(M)cd doc && texi2html -monolithic --init-file $(SRC_PATH_BARE)/doc/t2h.init $(<:doc/%=%)
 
 doc/%.pod: TAG = POD
 doc/%.pod: doc/%.texi

doc/developer.texi

@@ -2,11 +2,12 @@
 
 @settitle Developer Documentation
 @titlepage
-@sp 7
 @center @titlefont{Developer Documentation}
-@sp 3
 @end titlepage
 
+@top
+
+@contents
 
 @chapter Developers Guide
 

doc/faq.texi

@@ -2,11 +2,12 @@
 
 @settitle FFmpeg FAQ
 @titlepage
-@sp 7
 @center @titlefont{FFmpeg FAQ}
-@sp 3
 @end titlepage
 
+@top
+
+@contents
 
 @chapter General Questions
 

doc/ffmpeg.texi

@@ -2,11 +2,13 @@
 
 @settitle FFmpeg Documentation
 @titlepage
-@sp 7
 @center @titlefont{FFmpeg Documentation}
-@sp 3
 @end titlepage
 
+@top
+
+@contents
+
 @chapter Synopsis
 
 The generic syntax is:

doc/ffplay.texi

@@ -2,11 +2,13 @@
 
 @settitle FFplay Documentation
 @titlepage
-@sp 7
 @center @titlefont{FFplay Documentation}
-@sp 3
 @end titlepage
 
+@top
+
+@contents
+
 @chapter Synopsis
 
 @example

doc/ffprobe.texi

@@ -2,11 +2,13 @@
 
 @settitle FFprobe Documentation
 @titlepage
-@sp 7
 @center @titlefont{FFprobe Documentation}
-@sp 3
 @end titlepage
 
+@top
+
+@contents
+
 @chapter Synopsis
 
 The generic syntax is:

doc/ffserver.texi

@@ -2,11 +2,13 @@
 
 @settitle FFserver Documentation
 @titlepage
-@sp 7
 @center @titlefont{FFserver Documentation}
-@sp 3
 @end titlepage
 
+@top
+
+@contents
+
 @chapter Synopsys
 
 The generic syntax is:

doc/general.texi

@@ -2,11 +2,12 @@
 
 @settitle General Documentation
 @titlepage
-@sp 7
 @center @titlefont{General Documentation}
-@sp 3
 @end titlepage
 
+@top
+
+@contents
 
 @chapter external libraries
 

doc/libavfilter.texi

@@ -2,11 +2,12 @@
 
 @settitle Libavfilter Documentation
 @titlepage
-@sp 7
 @center @titlefont{Libavfilter Documentation}
-@sp 3
 @end titlepage
 
+@top
+
+@contents
 
 @chapter Introduction
 

doc/t2h.init

@@ -0,0 +1,24 @@
+# no horiz rules between sections
+$end_section = \&FFMPEG_end_section;
+sub FFMPEG_end_section($$)
+{
+}
+
+$print_page_foot = \&FFMPEG_print_page_foot;
+sub FFMPEG_print_page_foot($$)
+{
+    my $fh = shift;
+    print $fh "$SMALL_RULE\n";
+    T2H_DEFAULT_print_page_foot($fh);
+}
+
+# no navigation elements
+$SECTION_NAVIGATION = 0;
+# the same for texi2html 5.0
+$HEADERS = 0;
+
+# TOC and Chapter headings link
+$TOC_LINKS = 1;
+
+# print the TOC where @contents is used
+$INLINE_CONTENTS = 1;