runtime(r): Update R runtime files and docs (#13757)

* Update R runtime files
- Fix indentation issue with ggplot().
- Setlocal autoindent in indent/r.vim.
- New syntax option: rmd_include_latex.
- Clear syn iskeyword to recognize _ as keyword.
- Document some options.
- remove the test has("patch-7.4.1142")
- Update changed date of doc files

Signed-off-by: Jakson Alves de Aquino <jalvesaq@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org

runtime/doc/syntax.txt

@@ -1,4 +1,4 @@
-*syntax.txt*	For Vim version 9.0.  Last change: 2023 Dec 20
+*syntax.txt*	For Vim version 9.0.  Last change: 2023 Dec 23
 
 
 		  VIM REFERENCE MANUAL	  by Bram Moolenaar
@@ -2842,10 +2842,20 @@ To highlight R code in knitr chunk headers: >
 	let rmd_syn_hl_chunk = 1
 
 By default, chunks of R code will be highlighted following the rules of R
-language. If you want proper syntax highlighting of chunks of other languages,
-you should add them to either `markdown_fenced_languages` or
-`rmd_fenced_languages`. For example to properly highlight both R and Python,
-you may add this to your |vimrc|: >
+language. Moreover, whenever the buffer is saved, Vim scans the buffer and
+highlights other languages if they are present in new chunks. LaTeX code also
+is automatically recognized and highlighted when the buffer is saved. This
+behavior can be controlled with the variables `rmd_dynamic_fenced_languages`,
+and `rmd_include_latex` whose valid values are: >
+	let rmd_dynamic_fenced_languages = 0 " No autodetection of languages
+	let rmd_dynamic_fenced_languages = 1 " Autodetection of languages
+	let rmd_include_latex = 0 " Don't highlight LaTeX code
+	let rmd_include_latex = 1 " Autodetect LaTeX code
+	let rmd_include_latex = 2 " Always include LaTeX highlighting
+
+If the value of `rmd_dynamic_fenced_languages` is 0, you still can set the
+list of languages whose chunks of code should be properly highlighted, as in
+the example: >
 	let rmd_fenced_languages = ['r', 'python']