fix documentation for symlink

The target path is actually relative to the link, not to the current
working directory. This is in line with the ln shell command, so changing
the documentation to match the behavior seems in order.

Also changing some wording, and un-highlighting "symlink" throughout as
it never refers to the function.

std/file.d

@@ -2206,18 +2206,17 @@ unittest
 /++
     $(BLUE This function is Posix-Only.)
 
-    Creates a symlink.
+    Creates a symbolic _link (_symlink).
 
     Params:
-        original = The file to link from.
-        link     = The symlink to create.
-
-    Note:
-        Relative paths are relative to the current working directory,
-        not the files being linked to or from.
+        original = The file that is being linked. This is the target path that's
+            stored in the _symlink. A relative path is relative to the created
+            _symlink.
+        link = The _symlink to create. A relative path is relative to the
+            current working directory.
 
     Throws:
-        $(D FileException) on error (which includes if the symlink already
+        $(D FileException) on error (which includes if the _symlink already
         exists).
   +/
 version(StdDdoc) void symlink(C1, C2)(const(C1)[] original, const(C2)[] link) @safe;