Update README to mention LANGUAGES option, deprecate SINGLE_LANGUAGE

The LANGUAGES option covers a superset of the SINGLE_LANGUAGE option,
deprecate the latter.

CMakeLists.txt

@@ -15,9 +15,9 @@ project( KiCadDocumentation NONE )
 # Desired targets are DBLATEX,FOP and ASCIIDOCTOR-PDF
 set( PDF_GENERATOR "DBLATEX" CACHE STRING "Specify which PDF generator to use: DBLATEX|FOP" )
 
-# Provide an option for a single language build. If nothing else, this will at
-# least help developers to speed up a build they're working on
-set( SINGLE_LANGUAGE "" CACHE STRING "Specify a single language to build: en|fr|it|ja|nl|pl" )
+# Provide an option to limit the set of languages built. This helps developers to speed up a
+# build they're working on, or limit the number of dependencies for packagers
+set( LANGUAGES "" CACHE LIST "Specify languages to build: ca;de;en;es;fr;id;it;ja;nl;pl;ru;zh" )
 
 # Provide an option to decide which documentation formats to build.
 set( BUILD_FORMATS "html;pdf;epub" CACHE LIST "Specify which output formats to build html/pdf/epub" )

README.adoc

@@ -40,7 +40,7 @@ AsciiDoc documentation to other languages before the last compilation steps.
 * gettext >= 0.18
 * source-highlight
 * The _VL Gothic_ font is required when you build the Japanese PDFs. Look for a
-package named `fonts-vlgothic`. Otherwise use the SINGLE_LANGUAGE option
+package named `fonts-vlgothic`. Otherwise use the **LANGUAGES** option
 to avoid build errors.
 * For building PDF files with Cyrillic characters (like Russian) the fonts
 package _freefont-ttf_ is required, so you will need to look for similar named
@@ -115,17 +115,22 @@ e.g. `-DBUILD_FORMATS=html`
 When only one build format is enabled the package name is transformed to include
 the format.
 
-==== SINGLE_LANGUAGE
+==== LANGUAGES
 
 By default CMake will configure to build all languages available for each document.
 
-You can build just a single language by using the **SINGLE_LANGUAGE** option when
-configuring a build with CMake, e.g. `-DSINGLE_LANGUAGE=it`, etc.
+You can build just one or some of the languages by using the **LANGUAGES** option
+when configuring a build with CMake, e.g. `-DLANGUAGES=it;en;de`, etc.
 
-Currently, the available languages are : `en`, `fr`, `it`, `ja`, `nl`, and `pl` however, any
+Currently, the available languages are : `ca`, `de`, `en`, `es`, `fr`, `id`, `it`,
+`ja`, `nl`, `pl`, `ru`  and `zh`, however, any
 language code can be selected. Only translated documents will be built, so for
 some languages there may only be a partial documentation output.
 
+==== SINGLE_LANGUAGE
+
+This option is deprecated, use **LANGUAGES** instead
+
 When the **SINGLE_LANGUAGE** option is set, the package name is transformed to
 include the language.