Replace deprecated pandoc --self-contained option

"--embed-resources --standalone" is the recommended replacement. Fall
back to the deprecated option for old Pandoc versions that don't
support "--embed-resources".

Closes: #29

doc/meson.build

@@ -2,6 +2,13 @@ pdflatex = find_program('pdflatex', required: false)
 doc_style = files('style.css')[0]
 
 if pandoc.found()
+  if pandoc_version.version_compare('>=2.19')
+    self_contained = ['--embed-resources', '--standalone']
+  else
+    # old Pandoc, use now deprecated option
+    self_contained = ['--self-contained']
+  endif
+
   doc_meta = configure_file(input: 'mod_gnutls_manual.yaml.in',
 			    output: 'mod_gnutls_manual.yaml',
 			    configuration : conf_data)
@@ -31,7 +38,7 @@ if pandoc.found()
       doc_style],
     command : [
       pandoc, '--css', '@INPUT2@',
-      '--toc', '--self-contained',
+      '--toc', self_contained,
       '-f', 'markdown',
       '-o', '@OUTPUT@',
       '@INPUT0@', '@INPUT1@'],

meson.build

@@ -33,6 +33,11 @@ apache2 = declare_dependency(
 mod_dir = run_command(apxs, '-q', 'LIBEXECDIR', check: true).stdout().strip()
 
 pandoc = find_program('pandoc', required: false)
+if pandoc.found()
+  pandoc_version = run_command(
+    pandoc, '--version', check: true, capture: true).stdout().split()[1]
+  message('Found Pandoc version:', pandoc_version)
+endif
 httpd = find_program('apache2', 'httpd', dirs: ['/usr/sbin'], required: true)
 
 incdir = include_directories('include')