Fixed processing '\\' followed with a newline and line number output (-E) with it.

test/val/bug1891.c

@@ -0,0 +1,19 @@
+/* bug #1891 - backslash/newline sequence in string constants is treated wrong */
+
+#include <stdio.h>
+#include <string.h>
+
+const char* a = "hello \
+world";
+const char* b = \
+"hello world";
+
+int main(void)
+{
+    if (strcmp(a, b) != 0) {
+        printf("a:\n%s\n", a);
+        printf("b:\n%s\n", b);
+        return 1;
+    }
+    return 0;
+}