Add event and error identifiers to cli hashes cmd

test/cmdlineTests/hashes/args

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+--hashes

test/cmdlineTests/hashes/input.sol

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+// SPDX-License-Identifier: GPL-3.0
+pragma solidity >=0.0;
+
+error fileLevelError(uint z);
+
+library L {
+	event libraryEvent(uint r);
+	error libraryError(uint r);
+	error libraryErrorUnused(uint u);
+	event libraryEventUnused(uint u);
+}
+
+contract C {
+	struct S { uint x; }
+
+	event ev(uint y);
+	event anon_ev(uint y) anonymous;
+
+	error err(uint z, uint w);
+
+	function f(S memory s) public {
+		emit L.libraryEvent(3);
+		if (s.x > 1)
+			revert fileLevelError(3);
+		else
+			revert L.libraryError(4);
+	}
+}

test/cmdlineTests/hashes/output

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+
+======= hashes/input.sol:C =======
+Function signatures:
+3fc03eeb: f((uint256))
+
+Error signatures:
+619a0bb7: err(uint256,uint256)
+82b5f64f: fileLevelError(uint256)
+8c41f45c: libraryError(uint256)
+
+Event signatures:
+2d4dd5fe18ada5a020a9f5591539a8dc3010a5c074ba6a70e1c956659f02786a: ev(uint256)
+
+======= hashes/input.sol:L =======
+Function signatures:
+
+Error signatures:
+8c41f45c: libraryError(uint256)
+c61c03f5: libraryErrorUnused(uint256)
+
+Event signatures:
+81f3fb02f88d32d3bb08c80c9a622ca3b3223292f131c6ad049811f9a8a606dc: libraryEvent(uint256)
+0a994ad3600197f16ffe1ea1101caea3174efe5ebd9ba9a75d6d5524c5de28cd: libraryEventUnused(uint256)