tests: remove skip_test_ function; use new skip_ instead

* tests/init.cfg (skip_test_): Remove function.
Use skip_ in place of skip_test_ everywhere else.
* cfg.mk (sc_prohibit_skip_): Remove rule.
* tests/**: Use skip_, not skip_test_, everywhere.

tests/touch/dangling-symlink

@@ -34,7 +34,7 @@ if test $fail = 1; then
     *linux-gnu*)
       case "`uname -r`" in
         2.3.9[0-9]*)
-          skip_test_ \
+          skip_ \
 '****************************************************
 WARNING!!!
 This version of the Linux kernel causes touch to fail

tests/touch/no-dereference

@@ -41,7 +41,7 @@ test -f nowhere && fail=1
 # The remaining tests of -h require kernel support for changing symlink times.
 grep '^#define HAVE_UTIMENSAT 1' "$CONFIG_HEADER" > /dev/null ||
 grep '^#define HAVE_LUTIMES 1' "$CONFIG_HEADER" > /dev/null ||
-  skip_test_ 'this system lacks the utimensat function'
+  skip_ 'this system lacks the utimensat function'
 
 # Changing time of dangling symlink is okay.
 # Skip the test if this fails, but the error text corresponds to
@@ -51,7 +51,7 @@ case $? in
   0) test -f nowhere && fail=1
      test -s err && fail=1;;
   1) grep 'Function not implemented' err \
-       && skip_test_ 'this system lacks the utimensat function'
+       && skip_ 'this system lacks the utimensat function'
      fail=1;;
   *) fail=1;;
 esac

tests/touch/not-owner

@@ -21,11 +21,11 @@
 print_ver_ touch
 
 if env -- test -w /; then
-  skip_test_ you have write access to /.
+  skip_ you have write access to /.
 fi
 
 if env -- test -O / || env -- test -G /; then
-  skip_test_ "you own /."
+  skip_ "you own /."
 fi
 
 skip_if_root_