config: Show crosstool-NG version in .config

This was previously available in 6c62da4803 but was then removed
in cb7fcbe1ef. Add it back since it will be helpful if the user
wants to hide the crosstool-NG version in the pkgversion.

To get the new version, a defconfig from "ct-ng savedefconfig" or
"ct-ng oldconfig" must be used in combination with "ct-ng menuconfig"
or "ct-ng nconfig".

Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>

config/config.in

@@ -1,3 +1,4 @@
+mainmenu "crosstool-NG $CT_VERSION Configuration"
 source "config/configure.in"
 source "config/global.in"
 source "config/target.in"

config/global.in

@@ -1,5 +1,9 @@
 # Overall toolchain configuration: paths, jobs, etc...
 
+config CT_VERSION
+    string
+    option env="CT_VERSION"
+
 # Allow unconditional usage of tristates
 config MODULES
     bool