Add source locations to syntax test expectations.

test/libsolidity/syntaxTests/visibility/interface/function_default.sol

@@ -2,5 +2,5 @@ interface I {
 	function f();
 }
 // ----
-// Warning: Functions in interfaces should be declared external.
-// Warning: No visibility specified. Defaulting to "public". In interfaces it defaults to external.
+// Warning: (15-28): Functions in interfaces should be declared external.
+// Warning: (15-28): No visibility specified. Defaulting to "public". In interfaces it defaults to external.

test/libsolidity/syntaxTests/visibility/interface/function_default050.sol

@@ -3,5 +3,5 @@ interface I {
 	function f();
 }
 // ----
-// SyntaxError: No visibility specified.
-// TypeError: Functions in interfaces must be declared external.
+// SyntaxError: (45-58): No visibility specified.
+// TypeError: (45-58): Functions in interfaces must be declared external.

test/libsolidity/syntaxTests/visibility/interface/function_internal.sol

@@ -2,4 +2,4 @@ interface I {
 	function f() internal;
 }
 // ----
-// TypeError: Functions in interfaces cannot be internal or private.
+// TypeError: (15-37): Functions in interfaces cannot be internal or private.

test/libsolidity/syntaxTests/visibility/interface/function_private.sol

@@ -2,4 +2,4 @@ interface I {
 	function f() private;
 }
 // ----
-// TypeError: Functions in interfaces cannot be internal or private.
+// TypeError: (15-36): Functions in interfaces cannot be internal or private.

test/libsolidity/syntaxTests/visibility/interface/function_public.sol

@@ -2,4 +2,4 @@ interface I {
 	function f() public;
 }
 // ----
-// Warning: Functions in interfaces should be declared external.
+// Warning: (15-35): Functions in interfaces should be declared external.

test/libsolidity/syntaxTests/visibility/interface/function_public050.sol

@@ -3,4 +3,4 @@ interface I {
 	function f() public;
 }
 // ----
-// TypeError: Functions in interfaces must be declared external.
+// TypeError: (45-65): Functions in interfaces must be declared external.