Made kern a switching header file directory.

SConstruct:
    Put the code to make a switching header directory into a function so they are easy to make.
src/arch/SConscript:
    Replace switching header code with the new function call.
src/kern/SConscript:
    Created a new switching header directory in kern, and moved the declaration of some source files here.

--HG--
rename : src/kern/kernel_stats.cc => src/kern/base_kernel_stats.cc
rename : src/kern/kernel_stats.hh => src/kern/base_kernel_stats.hh
extra : convert_revision : 98f5320a5ade567c3e4f67fef123dfb0c5122545

src/arch/SConscript

@@ -63,36 +63,8 @@ isa_switch_hdrs = Split('''
 	vtophys.hh
         ''')
 
-# Generate the header.  target[0] is the full path of the output
-# header to generate.  'source' is a dummy variable, since we get the
-# list of ISAs from env['ALL_ISA_LIST'].
-def gen_switch_hdr(target, source, env):
-    fname = str(target[0])
-    basename = os.path.basename(fname)
-    f = open(fname, 'w')
-    f.write('#include "arch/isa_specific.hh"\n')
-    cond = '#if'
-    for isa in env['ALL_ISA_LIST']:
-        f.write('%s THE_ISA == %s_ISA\n#include "arch/%s/%s"\n'
-                % (cond, isa.upper(), isa, basename))
-        cond = '#elif'
-    f.write('#else\n#error "THE_ISA not set"\n#endif\n')
-    f.close()
-    return 0
-
-# String to print when generating header
-def gen_switch_hdr_string(target, source, env):
-    return "Generating ISA switch header " + str(target[0])
-
-# Build SCons Action object. 'varlist' specifies env vars that this
-# action depends on; when env['ALL_ISA_LIST'] changes these actions
-# should get re-executed.
-switch_hdr_action = Action(gen_switch_hdr, gen_switch_hdr_string,
-                           varlist=['ALL_ISA_LIST'])
-
-# Instantiate actions for each header
-for hdr in isa_switch_hdrs:
-    env.Command(hdr, [], switch_hdr_action)
+# Set up this directory to support switching headers
+env.make_switching_dir('arch', isa_switch_hdrs, env)
 
 #################################################################
 #