docs/manual: standardize references to the generic infra

Currently the text for each package infra that mentions the usage of
variables already provided by the generic infra diverge from each other:
- some (golang, kconfig, python) add a cross-referece to the generic
  infra chapter;
- kconfig does not list any example;
- some mention _LICENSE as an example, others don't;
- some (cargo, golang, python) add an 'etc.' at the end of the examples,
  giving the idea that can be more symbols provided by the generic
  infra than the ones listed;
- most have the text 'works by defining a number of variables before
  calling the +<macro-name>+ macro', except golang and kconfig;
- some actually list 'A few additional variables' but keep using some
  old reference as 'An additional variable';
- some say 'First, all the package metadata' and other only 'All the
  package metadata';
- most mention _SUBDIR as an example of variable supported by the
  generic infra, even the generic infra manual not mentioning it.

Improve the correctness for the manual by standardizing the text among
the package infras:
- use the same text "All the package metadata information variables that
  exist in the generic package infrastructure also exist in the
  <name> infrastructure:" for all of them;
- add the cross-reference for all of them;
- remove the examples of variables inherited from the generic infra -
  this also solves the _SUBDIR problem, there no longer is any reference
  to _SUBDIR;
- wrap the modified text at 80 columns;
- add "macro" to golang and luarocks infra;
- use "A few additional variables" for qmake and waf.

At same time, add a missing format on golang manual for
BR2_PACKAGE_HOST_GO_HOST_ARCH_SUPPORTS.

Cc: Eric Le Bihan <eric.le.bihan.dev@free.fr>
Cc: Thomas De Schampheleire <thomas.de_schampheleire@nokia.com>
Signed-off-by: Ricardo Martincoski <ricardo.martincoski@gmail.com>
[Arnout:
 - remove the examples;
 - add "the" where "macro" was added;
 - rewrite the preceding paragraphs for kconfig to make it more
   consistent.
]
Signed-off-by: Arnout Vandecappelle <arnout@mind.be>

docs/manual/adding-packages-python.adoc

@@ -80,10 +80,7 @@ or +host-python-package+ macros.
 
 All the package metadata information variables that exist in the
 xref:generic-package-reference[generic package infrastructure] also
-exist in the Python infrastructure: +PYTHON_FOO_VERSION+,
-+PYTHON_FOO_SOURCE+, +PYTHON_FOO_PATCH+, +PYTHON_FOO_SITE+,
-+PYTHON_FOO_SUBDIR+, +PYTHON_FOO_DEPENDENCIES+, +PYTHON_FOO_LICENSE+,
-+PYTHON_FOO_LICENSE_FILES+, +PYTHON_FOO_INSTALL_STAGING+, etc.
+exist in the Python infrastructure.
 
 Note that: