Update code style

There were some changes to code styling (via highlight.js) with the
update to Markdeep 1.15, plus we wanted to just revisit our code
styling, both in fenced blocks and inline.

Ultimately, I didn't find any improvement to our inline style.

For the general code style, I made preprocessor '#' characters and the
preprocessor keywords get the same styling. I also suppressed styling
for built-ins, parameters, types, and literals. I also tweaked the
background for deleted lines as well, to make it a bit more desaturated.

In addition, I've added book-highlight-test.css, which can be used to
identify the various syntactic elements for styling. See the header for
usage information.

Resolves #868
Resolves #1166

Author: hollasch

style/book-highlight-test.css

@@ -0,0 +1,69 @@
+/* -------------------------------------------------------------------------------------------------
+** Code Highlighting Style Test
+**
+** To use these test styles, go to the bottom of the Markdeep document and find the line containing
+**
+**     <link rel='stylesheet' href='../style/book.css'>
+**
+** Add this line following:
+**
+**     <link rel='stylesheet' href='../style/book-highlight-test.css'>
+**
+** -----------------------------------------------------------------------------------------------*/
+
+.md pre.listing.tilde {
+    border: solid 3px #d4d4d4;
+    padding: 1.5ex;
+    min-width: 96%;
+    width: fit-content;
+    background: #eee;
+}
+
+.md code {
+    /* All code, both in fenced blocks and inline. */
+    font-family: Consolas, Menlo, monospace;
+    font-size: 86%;
+    color: #000;
+    background: #eee;
+}
+
+.md pre.listing.tilde code {
+    /* Only code in fenced blocks. */
+    letter-spacing: -0.20;
+    background: #eee;
+}
+
+/* Hilight.js Syntax Coloring */
+
+.hljs-attr                 { color: #0ff; } /* Cyan Bright */
+.hljs-built_in             { color: #0cc; } /* Cyan */
+.hljs-comment              { color: #00f; } /* Blue */
+.hljs-doctag               { color: #fff; } /* White */
+.hljs-function .hljs-title { color: #f00; } /* Red */
+.hljs-keyword              { color: #0a0; } /* Green Dark */
+.hljs-literal              { color: #00a; } /* Blue Dark */
+.hljs-meta                 { color: #ff0; } /* Yellow Bright */
+.hljs-keyword              { color: #f0f; } /* Purple Bright */
+.hljs-meta .hljs-keyword   { color: #fa0; } /* Orange */
+.hljs-name                 { color: #0ff; font-weight: 900; } /* Cyan Bright Extra Bold */
+.hljs-number               { color: #f00; text-decoration: underline; } /* Red Underline */
+.hljs-operator             { color: #fff; } /* White */
+.hljs-params               { color: #f00; font-style: italic; } /* Red Italic */
+.hljs-string               { color: #aaa; } /* Gray */
+.hljs-tag                  { font-weight: 900; } /* Extra Bold */
+.hljs-title                { color: #b0b; } /* Purple Dark */
+.hljs-class_               { color: #0f0; } /* Green Bright */
+.hljs-type                 { color: #f00; font-weight: 900; } /* Red extra bold */
+
+/* Code Line Types */
+
+.md code > .highlight {
+    background-color: #ccdbc8;
+}
+
+.md code > .delete {
+    text-decoration: line-through;
+    background-color: #;
+    color: #a0a0a0;
+    background: #e0cfcc;
+}

style/book.css

@@ -101,10 +101,18 @@ div.indented {
 
 /* Hilight.js Syntax Coloring */
 
+.hljs-built_in, .hljs-params, .hljs-type, .hljs-literal {
+    color: #222;
+}
+
 .hljs-comment {
     color: #40f;
 }
 
+.hljs-meta .hljs-keyword {
+    color: #f40;
+}
+
 .hljs-keyword {
     color: #a62;
 }
@@ -131,7 +139,7 @@ div.indented {
     text-decoration: line-through;
     background-color: #;
     color: #a0a0a0;
-    background: #f4dcd8;
+    background: #e0cfcc;
 }
 
 .md div.listingcaption {