described --enable-debug and not only debug_info/flag

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_2_4_BRANCH@17928 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

docs/gtk/install.txt

@@ -73,7 +73,7 @@ such as for GTK and Motif, you can now build two complete libraries and use
 them concurrently. For this end, you have to create a directory for each build
 of wxWindows - you may also want to create different versions of wxWindows
 and test them concurrently. Most typically, this would be a version configured
-with --enable-debug_flag and one without. Note, that only one build can
+with --enable-debug and one without. Note, that only one build can
 currently be installed, so you'd have to use local version of the library for
 that purpose.
 
@@ -94,7 +94,7 @@ cd ..
 
 md buildgtkd
 cd buildgtkd
-../configure --with-gtk --enable-debug_flag
+../configure --with-gtk --enable-debug
 make
 cd ..
 
@@ -341,6 +341,12 @@ The following options handle the kind of library you want to build.
                             must be compiled with the same debug
                             options.
 
+    --enable-debug          Same as --enable-debug_info and
+                            --enable-debug_flag together. Unless you have
+                            some very specific needs, you should use this
+                            option instead of --enable-debug_info/flag ones
+                            separately.
+
 * Feature Options
 -----------------