docs: fix paragraph names for automake and aclocal invocations
All the other autotools entitle their invocation nodes
"autofoo Invocation", whereas automake used to call its
"Invoking Automake" and "Invoking aclocal". So let's
try to be more consistent.
This change is related to automake bug#8071.
Suggestion by Reuben Thomas and Eric Blake.
* doc/automake.texi (Invoking Automake): Node renamed ...
(automake Invocation): ... to this.
(Invoking aclocal): Node renamed ...
(aclocal Invocation): ... to this.
Add proper @anchor directives to avoid breaking existing web
hyperlinks still using the old names of the renamed nodes.