Switch back to SIGUSR1 for graceful restarts on all platforms that

support it.  This defines a symbol called AP_SIG_GRACEFUL in
ap_config_auto.h which will have the appropriate signal value.  All
direct references to SIGWINCH have been replaced with AP_SIG_GRACEFUL.

On Linux 2.0, use SIGWINCH instead since SIGUSR1 is used by glibc
2.0's user-space threading library to control threads.  All later
versions of Linux/glibc don't have this problem.  (Not to mention the
security holes in older Linux versions which make it unsuitable for
use as a web server.)  If your platform doesn't have SIGUSR1, use the
appropriate mojo in configure to define what your graceful restart
signal should be.

In theory, a configure switch could be added to allow the admin to
specify the appropriate signal that should be used.  This is left
as an exercise to the reader for now.

The docs need to be updated.  Since the signal is now configurable,
just saying SIGUSR1 for graceful restart isn't completely true.  Also,
the apachectl functionality needs to be moved into httpd - this is
what Win32 does and it makes us consistent across platforms.

Roy issued a veto against use of SIGWINCH by default, so this should
resolve that veto.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@91076 13f79535-47bb-0310-9956-ffa450edef68