New tel_read_header(), tel_read_body(). Use them in rea(),
show_first_tel(), copy_and_expire().
rea() now stops when it encounters a corrupt telegram, and logs the
problem. Before, error detection was incomplete, and errors were not
logged. Corrupt mailboxes could make it crash.
show_first_tel() and copy_and_expire() can now cope with telegrams of
arbitrary length, like rea(), and sanity-check the header fields they
don't actually use.
other. Ensure headers in include/ can be included in any order
(except for econfig-spec.h, which is special). New header types.h to
help avoid inclusion cycles. Sort include directives. Remove some
superflous includes.
between headers. Code is now fully prototyped and compiles cleanly
with gcc -Wstrict-prototypes -Wmissing-prototypes -Wnested-externs
-Wredundant-decls. Closes#723788.
