CC Mode: allow specified directives (e.g. pragma) to be indented as statements

CC Mode: allow specified directives (e.g. pragma) to be indented as statements

* lisp/progmodes/cc-cmds.el (c-align-cpp-indent-to-body)
(c-cpp-indent-to-body-flag, c-electric-pragma)
(c-add-indent-to-body-to-abbrev-table, c-clear-stale-indent-to-body-abbrevs)
(c-toggle-cpp-indent-to-body): New functions and variables.

* lisp/progmodes/cc-langs.el (c-std-abbrev-keywords): New lang const/var.

* lisp/progmodes/cc-mode.el (c-populate-abbrev-table): New function.
(c-basic-common-init): call the c-populate-abbrev-table.
(c-mode, c++-mode, objc-mode, java-mode, idl-mode, pike-mode, awk-mode):
Remove the setting of MODE-abbrev-table.

* lisp/progmodes/cc-vars.el (c-cpp-indent-to-body-directives): New defcustom.

* doc/misc/cc-mode.texi (Custom Macros): Introduce and refer to ....
(Indenting Directives): New page documenting the new mechanism.