basics/syntax: codify tab settings

Markdown.pl (incorrectly) expands hard tabs to spaces
using a tab stops set 4 spaces apart.

While it would be nice to fix this for code blocks, it
expands the tabs to spaces before doing anything else
so it would be non-trivial to do so.

Instead explain this deviant behavior in the help
files.

Signed-off-by: Kyle J. McKay <mackyle@gmail.com>

basics.text

@@ -38,7 +38,9 @@ A paragraph is simply one or more consecutive lines of text, separated
 by one or more blank lines. (A blank line is any line that looks like
 a blank line -- a line containing nothing but spaces or tabs is
 considered blank.) Normal paragraphs should not be indented with
-spaces or tabs.
+spaces or tabs. Note that Markdown expands all tabs to spaces using
+tabstops set at 4 spaces apart. It performs this expansion before
+doing anything else.
 
 Markdown offers two styles of headers: *Setext* and *atx*.
 Setext-style headers for `<h1>`, `<h2>` and `<h3>` are created by

syntax.text

@@ -187,6 +187,8 @@ A paragraph is simply one or more consecutive lines of text, separated
 by one or more blank lines. (A blank line is any line that looks like a
 blank line -- a line containing nothing but spaces or tabs is considered
 blank.) Normal paragraphs should not be indented with spaces or tabs.
+Note that Markdown expands all tabs to spaces using tabstops set at 4
+spaces apart. It performs this expansion before doing anything else.
 
 The implication of the "one or more consecutive lines of text" rule is
 that Markdown supports "hard-wrapped" text paragraphs. This differs