Let "make check" only check appropriate things

When configuring --without-ncat, "make check" was trying to run Ncat's
test suite. This commit splits the check target into ncat_check and
nsock_check, and makes each conditional on that subsystem's configure
status.

configure

@@ -631,9 +631,11 @@ NCAT_DIST_CLEAN
 NCAT_CLEAN
 NCAT_UNINSTALL
 NCAT_INSTALL
+NCAT_CHECK
 NCAT_BUILD
 NCATDIR
 LIBNSOCK_LIBS
+NSOCK_CHECK
 NSOCK_BUILD
 NSOCKDIR
 LIBNBASE_LIBS
@@ -7628,6 +7630,7 @@ subdirs="$subdirs nbase"
 
 NSOCKDIR="nsock"
 NSOCK_BUILD="nsock_build"
+NSOCK_CHECK="nsock_check"
 
 # Check whether --with-libnsock was given.
 if test "${with_libnsock+set}" = set; then :
@@ -7637,6 +7640,7 @@ if test "${with_libnsock+set}" = set; then :
   *)
     NSOCKDIR="$with_libnsock"
     NSOCK_BUILD=""
+    NSOCK_CHECK=""
     ;;
   esac
 
@@ -7651,6 +7655,7 @@ LIBNSOCK_LIBS="-lnsock"
 
 
 
+
 subdirs="$subdirs nsock/src"
 
 
@@ -7667,12 +7672,14 @@ fi
 
 if test "$with_ncat" = "no"; then
   NCAT_BUILD=""
+  NCAT_CHECK=""
   NCAT_INSTALL=""
   NCAT_UNINSTALL=""
   NCAT_CLEAN=""
   NCAT_DIST_CLEAN=""
 else
   NCAT_BUILD="ncat_build"
+  NCAT_CHECK="ncat_check"
   NCAT_INSTALL="install-ncat"
   NCAT_UNINSTALL="uninstall-ncat"
   NCAT_CLEAN="ncat_clean"
@@ -7690,6 +7697,7 @@ fi
 
 
 
+
 # Check whether --with-nmap-update was given.
 if test "${with_nmap_update+set}" = set; then :
   withval=$with_nmap_update;