'RELENG_7_0_0_RELEASE'.

This commit was manufactured to restore the state of the 7.0-RELEASE image.

setenv(3) by tracking the size of the memory allocated instead of using
strlen() on the current value.

Convert all calls to POSIX from historic BSD API:
 - unsetenv returns an int.
 - putenv takes a char * instead of const char *.
 - putenv no longer makes a copy of the input string.
 - errno is set appropriately for POSIX.  Exceptions involve bad environ
   variable and internal initialization code.  These both set errno to
   EFAULT.

Several patches to base utilities to handle the POSIX changes from
Andrey Chernov's previous commit.  A few I re-wrote to use setenv()
instead of putenv().

New regression module for tools/regression/environ to test these
functions.  It also can be used to test the performance.

Bump __FreeBSD_version to 700050 due to API change.

PR:		kern/99826
Approved by:	wes
Approved by:	re (kensmith)

Not because I admit they are technically wrong and not because of bug
reports (I receive nothing). But because I surprisingly meets so
strong opposition and resistance so lost any desire to continue that.

Anyone who interested in POSIX can dig out what changes and how
through cvs diffs.

don't allow const as putenv() arg, dup it

don't allow putenv() arg be on the stack, use strdup()

is needed in sysinstall on boot, but not in sade on a fully working system.

After this change I noticed no change in behavior on a vty when TERM is not
set.

Tested with:	make universe