use ~2.0 when depending on the locale component

Some methods have been added in 2.1 but none of them are used by the
Symfony components.

src/Symfony/Component/Form/composer.json

@@ -18,7 +18,7 @@
     "require": {
         "php": ">=5.3.3",
         "symfony/event-dispatcher": "2.2.*",
-        "symfony/locale": "2.2.*",
+        "symfony/locale": "~2.0",
         "symfony/options-resolver": "2.2.*",
         "symfony/property-access": "2.2.*"
     },

src/Symfony/Component/Validator/composer.json

@@ -21,7 +21,7 @@
     },
     "require-dev": {
         "symfony/http-foundation": "2.2.*",
-        "symfony/locale": "2.2.*",
+        "symfony/locale": "~2.0",
         "symfony/yaml": "~2.0",
         "symfony/config": "2.2.*"
     },