#4908 Make \header blocks tangible in Scheme

[David Kastrup]

Make \header blocks tangible in Scheme

This treats Guile modules and \header blocks as more or less
equivalent. Since \header blocks also contain module imports that
might not concur with those at the place of use, any use of a module
in place of a \header merely copies the values of the module
variables. Consists of the commits:

Admit \header-like expression into \score

Admit \header-like expressions in \header

Admit \header-like expressions at top levels

\header-like expressions are allowed at \book, \bookpart,
and top level.

Allow \header blocks in expressions

This allows creating modules for further programmatic manipulation.

http://codereview.appspot.com/296600043

[Anonymous]

Passes make, make check and a full make doc.

[David Kastrup]

Changes entry, identifiers regtest

http://codereview.appspot.com/296600043

[David Kastrup]

Use \markupId and \stringId in identifiers regtest

http://codereview.appspot.com/296600043

[Anonymous]

passes make, make check and a full make doc.

[Anonymous]

Patch on countdown for July 7th.

[Anonymous]

Patch counted down - please push

[David Kastrup]

Pushed to staging as
commit 4c8d9ad293aa114e851a4523d863d3194b6fe18f
Author: David Kastrup dak@gnu.org
Date: Wed Jun 29 18:58:11 2016 +0200

Issue 4908/7: Add Changes entry for \header expressions

commit 5d66f9b77ba36180ecaee91118e01c7f10cda1b2
Author: David Kastrup dak@gnu.org
Date: Thu Jun 30 12:23:50 2016 +0200

Issue 4908/6: Use \markupId and \stringId in identifiers regtest

commit f9c883f1a2eb08ca1da388ce1c0ebc1fb3556e5a
Author: David Kastrup dak@gnu.org
Date: Wed Jun 29 18:32:09 2016 +0200

Issue 4908/5: Add \header variables to `identifiers' regtest

commit 06732c99ce6ed25d7b8d43310cb4bb38b19fe27e
Author: David Kastrup dak@gnu.org
Date: Tue Jun 28 10:47:44 2016 +0200

Issue 4908/4: Admit \header-like expression into \score

commit 3571a1daacf4e1266a215171204f0a6df752c5cd
Author: David Kastrup dak@gnu.org
Date: Tue Jun 28 10:19:27 2016 +0200

Issue 4908/3: Admit \header-like expressions in \header

commit d5400b90987288185c5cbff9257c3a215ea84811
Author: David Kastrup dak@gnu.org
Date: Tue Jun 28 10:19:00 2016 +0200

Issue 4908/2: Admit \header-like expressions at top levels

\header-like expressions are allowed at \book, \bookpart,
and top level.

commit 92aa1b833f93c4daab52a547ff09cf9fee648ce4
Author: David Kastrup dak@gnu.org
Date: Tue Jun 28 09:11:45 2016 +0200

Issue 4908/1: Allow \header blocks in expressions

This allows creating modules for further programmatic manipulation.