ENGINE modules aren't special, so call them MODULES

The only thing that makes an ENGINE module special is its entry
points.  Other than that, it's a normal dynamically loadable module,
nothing special about it.  This change has us stop pretending anything
else.

We retain using ENGINE as a term for installation, because it's
related to a specific installation directory, and we therefore also
mark ENGINE modules specifically as such with an attribute in the
build.info files.

Reviewed-by: Nicola Tuveri <nic.tuv@gmail.com>
(Merged from https://github.com/openssl/openssl/pull/8147)
diff --git a/Configurations/README b/Configurations/README
index a106f8c..8efabb3 100644
--- a/Configurations/README
+++ b/Configurations/README
@@ -159,7 +159,7 @@
                            below [2].
         dso_scheme      => The type of dynamic shared objects to build
                            for.  This mostly comes into play with
-                           engines, but can be used for other purposes
+                           modules, but can be used for other purposes
                            as well.  Valid values are "DLFCN"
                            (dlopen() et al), "DLFCN_NO_H" (for systems
                            that use dlopen() et al but do not have
@@ -350,7 +350,7 @@
 
     - shared libraries; that would be libcrypto and libssl.
     - shared objects (sometimes called dynamic libraries);  that would
-      be the engines.
+      be the modules.
     - applications; those are apps/openssl and all the test apps.
 
     Very roughly speaking, linking is done like this (words in braces
@@ -411,10 +411,10 @@
 
     PROGRAMS=foo bar
     LIBS=libsomething
-    ENGINES=libeng
+    MODULES=libeng
     SCRIPTS=myhack
 
-Note that the files mentioned for PROGRAMS, LIBS and ENGINES *must* be
+Note that the files mentioned for PROGRAMS, LIBS and MODULES *must* be
 without extensions.  The build file templates will figure them out.
 
 For each thing to be built, it is then possible to say what sources