LanguageServers/Cpp: ParserAutoComplete engine inspects header files

... and performs preprocessing on the source code before parsing.

To support this, we are now able to keep track of multiple
files in the autocomplete engine. We re-parse a file whenever it is
edited.

Base/home/anon/Source/little/other.cpp

@@ -1,12 +1,13 @@
-#include <stdio.h>
 #include "other.h"
+#include <stdio.h>
 
 int func()
 {
     int x = 1;
     int y = 2;
+    StructInHeader mystruct;
     printf("x: %d\n", x);
     printf("y: %d\n", y);
-    printf("x+y: %d\n", x+y);
+    printf("x+y: %d\n", x + y);
     return x + y;
 }