More consistent catch statements

Also take const& in all cases.

libsolidity/formal/CVC4Interface.cpp

@@ -115,7 +115,7 @@ pair<CheckResult, vector<string>> CVC4Interface::check(vector<Expression> const&
 				values.push_back(toString(m_solver.getValue(toCVC4Expr(e))));
 		}
 	}
-	catch (CVC4::Exception & e)
+	catch (CVC4::Exception const&)
 	{
 		result = CheckResult::ERROR;
 		values.clear();

libsolidity/interface/StandardCompiler.cpp

@@ -600,7 +600,7 @@ string StandardCompiler::compile(string const& _input)
 		if (!jsonParseStrict(_input, input, &errors))
 			return jsonCompactPrint(formatFatalError("JSONError", errors));
 	}
-	catch(...)
+	catch (...)
 	{
 		return "{\"errors\":\"[{\"type\":\"JSONError\",\"component\":\"general\",\"severity\":\"error\",\"message\":\"Error parsing input JSON.\"}]}";
 	}
@@ -613,7 +613,7 @@ string StandardCompiler::compile(string const& _input)
 	{
 		return jsonCompactPrint(output);
 	}
-	catch(...)
+	catch (...)
 	{
 		return "{\"errors\":\"[{\"type\":\"JSONError\",\"component\":\"general\",\"severity\":\"error\",\"message\":\"Error writing output JSON.\"}]}";
 	}