Fix Key#inspect, Key#to_s, SubKey#inspect, & SubKey#to_s on 1.8.

* sprintf('%c', 'a') works fine on 1.9, but on 1.8 it raises "TypeError:
  can't convert String into Integer"

lib/gpgme/key.rb

@@ -208,7 +208,7 @@ module GPGME
     end
 
     def inspect
-      sprintf("#<#{self.class} %s %4d%c/%s %s trust=%s, owner_trust=%s, \
+      sprintf("#<#{self.class} %s %4d%s/%s %s trust=%s, owner_trust=%s, \
 capability=%s, subkeys=%s, uids=%s>",
               primary_subkey.secret? ? 'sec' : 'pub',
               primary_subkey.length,
@@ -224,7 +224,7 @@ capability=%s, subkeys=%s, uids=%s>",
 
     def to_s
       primary_subkey = subkeys[0]
-      s = sprintf("%s   %4d%c/%s %s\n",
+      s = sprintf("%s   %4d%s/%s %s\n",
                   primary_subkey.secret? ? 'sec' : 'pub',
                   primary_subkey.length,
                   primary_subkey.pubkey_algo_letter,

lib/gpgme/sub_key.rb

@@ -36,7 +36,7 @@ module GPGME
     end
 
     def inspect
-      sprintf("#<#{self.class} %s %4d%c/%s %s trust=%s, capability=%s>",
+      sprintf("#<#{self.class} %s %4d%s/%s %s trust=%s, capability=%s>",
               secret? ? 'ssc' : 'sub',
               length,
               pubkey_algo_letter,
@@ -47,7 +47,7 @@ module GPGME
     end
 
     def to_s
-      sprintf("%s   %4d%c/%s %s\n",
+      sprintf("%s   %4d%s/%s %s\n",
               secret? ? 'ssc' : 'sub',
               length,
               pubkey_algo_letter,

test/key_test.rb

@@ -183,5 +183,19 @@ describe GPGME::Key do
 
     assert key.expired
   end
+
+  describe :inspect do
+    it "can be inspected" do
+      key = GPGME::Key.find(:secret).first
+      key.inspect
+    end
+  end
+
+  describe :to_s do
+    it "can be coerced into a String" do
+      key = GPGME::Key.find(:secret).first
+      key.to_s
+    end
+  end
 end
 

test/sub_key_test.rb

@@ -28,4 +28,18 @@ describe GPGME::SubKey do
     end
   end
 
+  describe :inspect do
+    it "can be inspected" do
+      subkey = GPGME::Key.find(:secret).first.primary_subkey
+      subkey.inspect
+    end
+  end
+
+  describe :to_s do
+    it "can be coerced into a String" do
+      subkey = GPGME::Key.find(:secret).first.primary_subkey
+      subkey.to_s
+    end
+  end
+
 end