Added escape sequences

tests/programs/escape-rune.q

@@ -0,0 +1,9 @@
+main() {
+	assert '\0' == 0
+	assert '\t' == 9
+	assert '\n' == 10
+	assert '\r' == 13
+	assert '\"' == 34
+	assert '\'' == 39
+	assert '\\' == 92
+}

tests/programs/escape-string.q

@@ -0,0 +1,10 @@
+main() {
+	str := "\0\t\n\r\"\'\\"
+	assert str[0] == '\0'
+	assert str[1] == '\t'
+	assert str[2] == '\n'
+	assert str[3] == '\r'
+	assert str[4] == '\"'
+	assert str[5] == '\''
+	assert str[6] == '\\'
+}