Add checker for MarkdownPP failures; fix existing failures (fixes #1497)

MarkdownPP fails on broken ``` code sections.

Documentation/Books/Makefile

@@ -31,6 +31,15 @@ book-check-restheader-leftovers:
 		exit 1; \
 	fi
 
+# Check for all lines starting with exclamation marks, except image links which are exclamation mar + bracket
+book-check-mdpp-leftovers:
+	@if test "`find ppbooks/$(NAME) -name '*.md' -exec grep -- '^![^\[]' {} \; -print | wc -l`" -gt 0; then \
+		echo "found these unconverted Markdown-PP tags: "; \
+		find ppbooks/$(NAME) -name '*.md' -exec grep '^![^\[]' {} \; -print; \
+		exit 1; \
+	fi
+
+
 book-check-markdown-leftovers:
 	@if test "`find books/$(NAME) -name '*.html' -exec grep -- '##' {} \; -print | wc -l`" -gt 0; then \
 		echo "found these unconverted markdown titles: "; \
@@ -79,6 +88,7 @@ build-book:
 	make check-summary
 	make book-check-leftover-docublocks
 	make book-check-restheader-leftovers
+	make book-check-mdpp-leftovers
 
 	cd ppbooks/$(NAME) && gitbook install
 	cd ppbooks/$(NAME) && gitbook build ./ ./../../books/$(NAME)

Documentation/Books/Users/AqlExtending/Conventions.mdpp

@@ -8,7 +8,7 @@ function groups if required.
 
 Examples:
 
-``` js
+```
 RETURN myfunctions::myfunc()
 
 RETURN myfunctions::math::random()
@@ -43,6 +43,7 @@ effects when executing the function.
 
 Here is an example that may modify outer scope variables `i` and `name`,
 making the function **not** side effects-free:
+
 ``` js
 function (values) {
   for (i = 0; i < values.length; ++i) {
@@ -57,6 +58,7 @@ function (values) {
 
 The above function can be made free of side effects by using the `var`
 keyword, so the variables become function-local variables:
+
 ``` js
 function (values) {
   for (var i = 0; i < values.length; ++i) {
@@ -81,5 +83,6 @@ to undefined behavior and should be avoided.
 
 Internally, user functions are stored in a system collection named
 *_aqlfunctions*. That means that by default they are excluded from dumps
-created with [arangodump](../HttpBulkImports/Arangodump.md). To include AQL user functions in a dump, the
-dump should be started with the option *--include-system-collections true*.
+created with [arangodump](../HttpBulkImports/Arangodump.md).
+To include AQL user functions in a dump, the dump should be started
+with the option *--include-system-collections true*.

Documentation/Books/Users/ModuleProcess/README.mdpp

@@ -8,16 +8,16 @@ env maps the systems environment to an associative array.
 
 <!--
 these are copied from node, but don't serve any specific purpose over here
-! SUB SECTION domain
+x! SUB SECTION domain
 
 
-! SUB SECTION _events
+x! SUB SECTION _events
 
-! SUB SECTION argv
+x! SUB SECTION argv
 
-! SUB SECTION stdout
+x! SUB SECTION stdout
 
-! SUB SECTION CMD
+x! SUB SECTION CMD
 
-! SUB SECTION nextTick
+x! SUB SECTION nextTick
 -->