fix HTML problems associated with leading ---'s

Please do not use "**---**" in markdown lines to separate sections.

This causes `pandoc(1)` to generate "**\<hr />**".

The "**\<hr />**" has no effect in standard HTML 5 and interacts
badly with unquoted attribute values.

If a horizontal line is really needed, use "**\<hr>**".

If a short line is needed, use: "**\<hr
style="width:10%;text-align:left;margin-left:0">**"

2013/hou/README.md

@@ -150,8 +150,13 @@ header has a comment line for non-standard-compliant viewers (specifically, my
 old HDRShop 1.0). And there is a nice text message saying "please wait...".
 Despite the messy look, [a.c](a.c) and [hou.c](hou.c) compile warning-free
 ([hou.c](hou.c) even wastes 18 bytes on `#include<stdio.h>` just for `putchar(3)`).
-[a.c](a.c) compiles mostly clean in the C99/ANSI modes of clang and gcc (with `-Wall
---pedantic`). The only warning generated is a pedantic one: `"string constant
+[a.c](a.c) compiles mostly clean in the C99/ANSI modes of clang and gcc (with:
+
+```
+-Wall --pedantic
+```
+
+The only warning generated is a pedantic one: `"string constant
 too long"`.