meson: use booleans for conf.set and drop unecessary conditionals

Using conf.set() with a boolean argument does the right thing:
either #ifdef or #undef. This means that conf.set can be used unconditionally.

Previously I used '1' as the placeholder value, and that needs to be changed to
'true' for consistency (under meson 1 cannot be used in boolean context). All
checks need to be adjusted.

docs/sysvinit/meson.build

@@ -3,7 +3,7 @@ file = configure_file(
         output : 'README',
         configuration : substs)
 
-if conf.get('HAVE_SYSV_COMPAT', 0) == 1
+if conf.get('HAVE_SYSV_COMPAT', false)
         install_data(file,
                      install_dir : sysvinit_path)
 endif

docs/var-log/meson.build

@@ -3,7 +3,7 @@ file = configure_file(
         output : 'README',
         configuration : substs)
 
-if conf.get('HAVE_SYSV_COMPAT', 0) == 1
+if conf.get('HAVE_SYSV_COMPAT', false)
         install_data(file,
                      install_dir : varlogdir)
 endif

hwdb/meson.build

@@ -17,7 +17,7 @@ hwdb_files = files('''
         70-touchpad.hwdb
 '''.split())
 
-if conf.get('ENABLE_HWDB', 0) == 1
+if conf.get('ENABLE_HWDB', false)
         install_data(hwdb_files,
                      install_dir : udevhwdbdir)
 

man/meson.build

@@ -50,7 +50,7 @@ foreach tuple : manpages
 
         mandirn = join_paths(get_option('mandir'), 'man' + section)
 
-        if condition == '' or conf.get(condition, 0) == 1
+        if condition == '' or conf.get(condition, false)
                 p1 = custom_target(
                         man,
                         input : xml,