[math/big] Rename internal_int_shl_digit to _private_int_shl_leg.

Same for the SHR variant. These are pure implementation details to shift by a leg/word at a time.
Prevent accidental usage.

core/math/big/logical.odin

@@ -86,21 +86,6 @@ int_shr :: proc(dest, source: ^Int, bits: int, allocator := context.allocator) -
 }
 shr :: proc { int_shr, }
 
-/*
-	Shift right by `digits` * _DIGIT_BITS bits.
-*/
-int_shr_digit :: proc(quotient: ^Int, digits: int, allocator := context.allocator) -> (err: Error) {
-	/*
-		Check that `quotient` is usable.
-	*/
-	assert_if_nil(quotient)
-	context.allocator = allocator
-
-	internal_clear_if_uninitialized(quotient) or_return
-	return #force_inline internal_int_shr_digit(quotient, digits)
-}
-shr_digit :: proc { int_shr_digit, }
-
 /*
 	Shift right by a certain bit count with sign extension.
 */
@@ -124,20 +109,4 @@ int_shl :: proc(dest, src: ^Int, bits: int, allocator := context.allocator) -> (
 	internal_clear_if_uninitialized(dest, src) or_return
 	return #force_inline internal_int_shl(dest, src, bits)
 }
-shl :: proc { int_shl, }
-
-
-/*
-	Shift left by `digits` * _DIGIT_BITS bits.
-*/
-int_shl_digit :: proc(quotient: ^Int, digits: int, allocator := context.allocator) -> (err: Error) {
-	/*
-		Check that `quotient` is usable.
-	*/
-	assert_if_nil(quotient)
-	context.allocator = allocator
-
-	internal_clear_if_uninitialized(quotient) or_return
-	return #force_inline internal_int_shl_digit(quotient, digits)
-}
-shl_digit :: proc { int_shl_digit, };
+shl :: proc { int_shl, }