doc: Fix asciidoc escapes for C++ (#1427)

Signed-off-by: Stefan Weil <sw@weilnetz.de>

Author: stweil

doc/tesseract.1.asc

@@ -343,9 +343,9 @@ HISTORY
 -------
 The engine was developed at Hewlett Packard Laboratories Bristol and at
 Hewlett Packard Co, Greeley Colorado between 1985 and 1994, with some more
-changes made in 1996 to port to Windows, and some C\+\+izing in 1998. A
-lot of the code was written in C, and then some more was written in C\+\+.
-The C++ code makes heavy use of a list system using macros. This predates
+changes made in 1996 to port to Windows, and some $$C++$$izing in 1998. A
+lot of the code was written in C, and then some more was written in $$C++$$.
+The $$C++$$ code makes heavy use of a list system using macros. This predates
 stl, was portable before stl, and is more efficient than stl lists, but has
 the big negative that if you do get a segmentation violation, it is hard to
 debug.