Feature/fix email From: w/ configurable "displayname" (#17)

Feature/fix email From: w/ configurable "displayname" (#17)

* WIP: add displayname option

Signed-off-by: Marco Emilio "sphakka" Poleggi <7766137+sphakka@users.noreply.github.com>
* Fix configure.in

Signed-off-by: Marco Emilio "sphakka" Poleggi <7766137+sphakka@users.noreply.github.com>
* Restored orig configure.in + displayname opt

Signed-off-by: Marco Emilio "sphakka" Poleggi <7766137+sphakka@users.noreply.github.com>
* job.c: create_mail():

Process 'displayname', etc. via new function 'make_mailbox()' as per RFC5322.

Signed-off-by: Marco Emilio "sphakka" Poleggi <7766137+sphakka@users.noreply.github.com>
* Fixed wrong formatting (tabs => spaces)

Signed-off-by: Marco Emilio "sphakka" Poleggi <7766137+sphakka@users.noreply.github.com>
* dev(code, doc, test): displayname handling refactored over two functions.

* code: config handling of displayname moved to a new function
  'format_displayname()' in 'fcronconf.c'; buffer overflow check added. In
  'job.c': restored old "From:" mail header behavior if no displayname; buffer
  overflow check added.
* test: added prototype support in 'Makefile' and 'test/'
* doc: reviewed and cleaned 'en/fcron.conf.5.sgml'

Signed-off-by: Marco Emilio "sphakka" Poleggi <7766137+sphakka@users.noreply.github.com>
* dev(code, test): @PR #17, 3rd round.

* Makefile(s): fixed alignement with spaces
* config.in: moved displayname in "Check for fcron..." section. Removed test
    install code.
* fcronconf.c: changed format_displayname()'s arg to avoid confusion with
    globals. Use stdbool. Use aux var when assigning from
    format_displayname().
* crondyn_svr.c, fileconf.c: minimal fixes to avoid conflict with stdbool.
* fcron.conf.in: added comment for possible displayname's future default value.
* global.h: added stdbool.
* job.c: changed make_mailbox_addr()'s arg to avoid confusion with
    globals. Use stdbool.
* test/mailbox_addr.c: rewritten with simpler explicit logic -- valgrinded
    again ;-)

Signed-off-by: Marco Emilio "sphakka" Poleggi <7766137+sphakka@users.noreply.github.com>
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Signed-off-by: Marco Emilio "sphakka" Poleggi <7766137+sphakka@users.noreply.github.com>