Misc small fixes to suppress warnings.

Code should now be clean with msvc /W4 and gcc /Wall /Wextra -pedantic with the exception of one deliberate warning in one test.

[SVN r57510]

test/implicit_cast.cpp

@@ -28,5 +28,11 @@ int main()
 
     type<foo> f = check_return(boost::implicit_cast<foo>("hello"));
     type<long> z = check_return(boost::implicit_cast<long>(foo("hello")));
+    
+    // warning supression:
+    (void)x;
+    (void)f;
+    (void)z;
+
     return boost::report_errors();
 }

test/implicit_cast_fail.cpp

@@ -19,4 +19,6 @@ struct foo
 int test_main(int, char*[])
 {
     foo x = implicit_cast<foo>("foobar");
+    (void)x;  // warning suppression.
+    return 0;
 }

test/lexical_cast_abstract_test.cpp

@@ -51,7 +51,7 @@ std::ostream &operator<<(std::ostream &O, const A &a)
 {
     a.out(O);
     return O;
-};
+}
 
 void test_abstract()
 {