ntp: re-enable server debugging and control by PACKAGECONFIG

The description in a previous patch to disable debugging is incorrect.
Although the option is default-enabled in configure.ac, configure does
respect the option that disables it.

In ntp 4.2.7 the option code is refactored to ntp_debug.m4 and has an
effect in sntp as well.  Adding --disable-debugging to the top-level
configure options overrides the default for both 4.2.6 and 4.2.7 without
patching the distribution.

Make the selection explicit and configurable, but restore the historical
default.  Absence of debugging capability in the server makes it
difficult to validate complex configurations.

Signed-off-by: Peter A. Bigot <pab@pabigot.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>

meta-networking/recipes-support/ntp/files/ntp-disable-debugging.patch

@@ -1,23 +0,0 @@
-set ntp_ok to no if ntp debugging is not enabled.
-
-Upstream-status: Pending
-
-There is a problem in configure.ac file that whether or not
-'--enable-debugging' is specified in configure cmdline, debugging
-is always enabled.
-We should disable ntp debugging by default.
-
-Signed-off-by: Xufeng Zhang <xufeng.zhang@windriver.com>
-
----
---- a/configure.ac
-+++ b/configure.ac
-@@ -2458,7 +2458,7 @@
-         [+ include ntpd debugging code]
-     )],
-     [ntp_ok=$enableval],
--    [ntp_ok=yes]
-+    [ntp_ok=no]
- )
- case "$ntp_ok" in
-  yes)

meta-networking/recipes-support/ntp/ntp.inc

@@ -23,7 +23,6 @@ SRC_URI = "http://www.eecis.udel.edu/~ntp/ntp_spool/ntp4/ntp-4.2/ntp-${PV}.tar.g
            file://sntp.service \
            file://sntp \
            file://ntpd.list \
-           file://ntp-disable-debugging.patch \
            file://CVE-2013-5211.patch \
 "
 
@@ -38,7 +37,8 @@ USERADD_PACKAGES = "${PN}"
 USERADD_PARAM_${PN} = "--system --home-dir /var/lib/ntp \
                        --shell /bin/false --user-group ntp"
 
-PACKAGECONFIG ??= "cap"
+# NB: debug is default-enabled by NTP; keep it default-enabled here.
+PACKAGECONFIG ??= "cap debug"
 PACKAGECONFIG[openssl] = "--with-openssl-libdir=${STAGING_LIBDIR} \
                           --with-openssl-incdir=${STAGING_INCDIR} \
                           --with-crypto, \
@@ -46,6 +46,7 @@ PACKAGECONFIG[openssl] = "--with-openssl-libdir=${STAGING_LIBDIR} \
                           openssl"
 PACKAGECONFIG[cap] = "--enable-linuxcaps,--disable-linuxcaps,libcap"
 PACKAGECONFIG[readline] = "--with-lineeditlibs,--without-lineeditlibs,readline"
+PACKAGECONFIG[debug] = "--enable-debugging,--disable-debugging"
 
 do_install_append() {
     install -d ${D}${sysconfdir}/init.d