parser.c: Remove ASCII_XXX definitions, use those from string_internal.h

In parser.c remove these:
```C
#define  ASCII_TAB    (0x09)
#define  ASCII_DASH   (0x2D)
#define  ASCII_GT     (0x3E)
#define  ASCII_DASH   (0x2D)
```
And wherever they are used, use corresponding values from string_internal.h