Update documentation files.
diff --git a/runtime/doc/vimtutor.1 b/runtime/doc/vimtutor.1
index 12bde7e..0aa7e8d 100644
--- a/runtime/doc/vimtutor.1
+++ b/runtime/doc/vimtutor.1
@@ -3,7 +3,7 @@
vimtutor \- the Vim tutor
.SH SYNOPSIS
.br
-.B vimtutor [-g] [language]
+.B vimtutor [\-g] [language]
.SH DESCRIPTION
.B Vimtutor
starts the
@@ -18,7 +18,7 @@
.B Vim
commands.
.PP
-The optional argument -g starts vimtutor with gvim rather than vim, if the
+The optional argument \-g starts vimtutor with gvim rather than vim, if the
GUI version of vim is available, or falls back to Vim if gvim is not found.
.PP
The optional [language] argument is the two-letter name of a language, like