Preprocessor directives can now appear in the argument list of function-like macro calls.

#pragma PP-tokens can now be macro replaced.
#include header names directly enclosed in <> are free of macro replacement.
Preprocess-only mode (-E) now outputs with #line as source info.
Moved testcases for #760 and #1357.
Added testcase for #1643.

test/val/bug1643.h

@@ -0,0 +1,13 @@
+/* bug #1643, macro expansion in #include */
+
+#define STDIO_H     <stdio.h>
+#include STDIO_H
+
+#ifdef string
+#undef string
+#endif
+
+#define string      0!%^&*/_=
+#include <string.h>
+
+#define BUG1643_RESULT 0