Improved English.

auto/help

@@ -7,20 +7,20 @@ cat << END
 
 ./configure options:
 
-  --cc=FILE            set C compiler file name, default: $CC
+  --cc=FILE            set C compiler filename, default: "$CC"
   --cc-opt=OPTIONS     set additional C compiler options
   --ld-opt=OPTIONS     set additional linker options
 
-  --prefix=DIRECTORY   set prefix for relative path names, no by default
-  --pid=FILE           set pid file name, default: $NXT_PID
-  --log=FILE           set log file name, default: $NXT_LOG
-  --modules=DIRECTORY  set modules directory, default: $NXT_MODULES
+  --prefix=DIRECTORY   set prefix for relative pathnames, default: none
+  --pid=FILE           set pid filename, default: "$NXT_PID"
+  --log=FILE           set log filename, default: "$NXT_LOG"
+  --modules=DIRECTORY  set modules directory name, default: "$NXT_MODULES"
 
   --control=ADDRESS    set address of control API socket
-                       default: $NXT_CONTROL
+                       default: "$NXT_CONTROL"
 
   --user=USER          set non-privileged processes to run as specified user
-                       default: $NXT_USER
+                       default: "$NXT_USER"
   --group=GROUP        set non-privileged processes to run as specified group
                        default: user's primary group