Change library suffix from _debug to D for debug build.

And no suffix for a release build.

SConstruct

@@ -74,6 +74,7 @@ assertions = GetOption('assertions')
 stack_protection = GetOption('stack_protection')
 test_xml = GetOption('test_xml')
 prefix = GetOption('prefix')
+lib_suffix = ''
 if not (build_type in ['debug', 'release']):
     print "Error: expected 'debug' or 'release', found: " + build_type
     Exit(1)
@@ -111,6 +112,7 @@ if build_type == 'release':
         env.Append(CPPDEFINES = ['NDEBUG'])
 
 elif build_type == 'debug':
+    lib_suffix = 'D'
     env.Append(CPPDEFINES = ['DEBUG'])
 
 if stack_protection:
@@ -132,7 +134,7 @@ if stack_protection:
 
 subst_info['@build_host@'] = platform.node()
 
-Export('env', 'build_type', 'prefix', 'version_info', 'test_xml', 'subst_info')
+Export('env', 'build_type', 'prefix', 'lib_suffix', 'version_info', 'test_xml', 'subst_info')
 
 #put all .sconsign files in one place
 env.SConsignFile()