Shift selection of debug-level

Currently configure switches on gcc to debug mode what means -O0. Adding
-d none does not help because it is filtered out earlier. -d bla would
help if bla were an allowed keyword.
This patch simply shifts the "compiler is gcc" block to the left so -O2 is
selected if the user selected -d none on the command line. Other compilers
remain with no extra switches.

wscript

@@ -181,7 +181,6 @@ def configure (conf):
             debug_level = 'debug'
         else:
             debug_level = 'none'
-    if debug_level != 'none':
     if compiler == 'gcc':
         if debug_level == 'debug':
             conf.env.append_value ('CCFLAGS', '-Wall -O0 -g'.split ())
@@ -202,7 +201,7 @@ def configure (conf):
                 '-DG_ENABLE_DEBUG'.split ())
         else:
             conf.env.append_value ('CCFLAGS', '-O2')
-        else:
+    elif debug_level != 'none':
             Utils.pprint ('RED', 'No debugging level support for ' + compiler)
             sys.exit (1)