Fix documentation links

Ensure that all links on diffblue.github.io/cbmc/ resolve to an existing
page. Fixes the reported issue (#7450) as well as others found by
running
`wget --spider -r -nd -nv --level 10 https://diffblue.github.io/cbmc/`.

Fixes: #7450

Author: tautschnig

doc/doxygen-root/user_guide.md

@@ -3,7 +3,7 @@
 For a quick start with CBMC on simple problems, read
 
 * The \ref installation_guide
-* A [short tutorial](cprover-manual/md_cbmc-tutorial.html)
+* A [short tutorial](cprover-manual/md_cbmc_tutorial.html)
 * A [short manual](cprover-manual/index.html)
 
 For a quick start with CBMC on large software projects, read
@@ -23,7 +23,7 @@ Key concepts:
 
 * The \ref reference_guide describes CBMC and the CBMC tool chain
 * CBMC [primitives](cprover-manual/md_api.html) and
-  [memory primitives](cprover-manual/md_memory-primitives.html)
+  [memory primitives](cprover-manual/md_memory_primitives.html)
   are useful when writing CBMC assumptions and CBMC assertions.
 * \ref goto-programs "goto programs" are the intermediate representation
   of C code used by the CBMC tool chain

doc/satabs-user-manual.md

@@ -57,7 +57,7 @@ and the directories that contain the header files. You must run SATABS
 from within the *Visual Studio Command Prompt*.
 
 Note that the distribution files for the [Eclipse
-plugin](installation-plugin.shtml) include the command-line tools.
+plugin](http://www.cprover.org/eclipse-plugin/) include the command-line tools.
 Therefore, if you intend to run SATABS exclusively within Eclipse, you
 can skip the installation of the command-line tools. However, you still
 have to install the compiler environment as described above.