Switch the default latex variant to xelatex.

The pg environment variable is now `$externalPrograms{latex2pdf}`.
This was changed as discussed in the development meeting today because
it is odd for it to be named pdflatex if we are not using pdflatex, and
to match the corresponding webwork2 change.

Author: drgrice1

conf/pg_config.dist.yml

@@ -86,7 +86,7 @@ externalPrograms:
   curl: /usr/bin/curl
   tar: /bin/tar
   latex: /usr/bin/latex --no-shell-escape
-  pdflatex: /usr/bin/pdflatex --no-shell-escape
+  latex2pdf: /usr/bin/xelatex --no-shell-escape
   dvisvgm: /usr/bin/dvisvgm
   pdf2svg: /usr/bin/pdf2svg
   convert: /usr/bin/convert

lib/LaTeXImage.pm

@@ -214,8 +214,8 @@ sub draw {
 			print $fh $self->footer;
 			close $fh;
 			system "cd $working_dir && "
-				. WeBWorK::PG::IO::externalCommand('pdflatex')
-				. " --interaction=nonstopmode image.tex > pdflatex.stdout 2> /dev/null";
+				. WeBWorK::PG::IO::externalCommand('latex2pdf')
+				. " --interaction=nonstopmode image.tex > latex.stdout 2> /dev/null";
 			chmod(0777, "$working_dir/image.pdf");
 		} else {
 			warn "Can't open $working_dir/image.tex for writing.";
@@ -251,7 +251,7 @@ sub draw {
 			}
 		} else {
 			warn "The pdf file was not created.";
-			if (open(my $err_fh, "<", "$working_dir/pdflatex.stdout")) {
+			if (open(my $err_fh, "<", "$working_dir/latex.stdout")) {
 				while (my $error = <$err_fh>) {
 					warn $error;
 				}

macros/core/PGbasicmacros.pl

@@ -2896,7 +2896,7 @@ sub image {
 		if ($displayMode eq 'TeX') {
 			my $imagePath = $imageURL;    # in TeX mode, alias gives us a path, not a URL
 
-			# We're going to create PDF files with our TeX (using pdflatex), so
+			# We're going to create PDF files with our TeX (using LaTeX), so
 			# alias should have given us the path to a PNG image.
 			if ($imagePath) {
 				if ($valign eq 'top') {