Unified use of settings. Removed a couple of unused functions.

test/libsolidity/semanticTests/viaYul/detect_mod_zero.sol

@@ -7,7 +7,7 @@ contract C {
     }
 }
 // ====
-// compileViaYul: only
+// compileViaYul: true
 // ----
 // f(uint256,uint256): 10, 3 -> 1
 // f(uint256,uint256): 10, 2 -> 0

test/libsolidity/semanticTests/viaYul/detect_mod_zero_signed.sol

@@ -7,7 +7,7 @@ contract C {
     }
 }
 // ====
-// compileViaYul: only
+// compileViaYul: true
 // ----
 // f(int256,int256): 10, 3 -> 1
 // f(int256,int256): 10, 2 -> 0

test/libsolidity/semanticTests/viaYul/keccak.sol

@@ -8,7 +8,7 @@ contract C {
     }
 }
 // ====
-// compileViaYul: only
+// compileViaYul: true
 // ----
 // keccak1() -> 0x64e604787cbf194841e7b68d7cd28786f6c9a0a3ab9f8b0a0e87cb4387ab0107
 // keccak2() -> 0x64e604787cbf194841e7b68d7cd28786f6c9a0a3ab9f8b0a0e87cb4387ab0107

test/libsolidity/semanticTests/viaYul/string_format.sol

@@ -5,7 +5,7 @@ contract C {
 	function h() external pure returns (bytes4) { return 0xcafecafe; }
 }
 // ====
-// compileViaYul: only
+// compileViaYul: true
 // ----
 // f1() -> 0x20, 6, left(0x616263616263)
 // f2() -> 32, 47, 44048183223289766195424279195050628400112610419087780792899004030957505095210, 18165586057823232067963737336409268114628061002662705707816940456850361417728