Fix #684: Keep line directives in tokenized output

[glankk]

The lineDirective function is not really needed after this change and has been removed. A locationchange flag has been added to the Token class to keep track of when a location discontinuity occurs, this is needed for gotoNextLine to still work correctly during preprocessing when #line moves back to the same line it is already at.

[glankk]

There are some issues with how simplecpp currently handles directives and locations with respect to lines. The sameline function that is used in many places only checks the logical location of tokens which is affected by line directives. So for example, the following was until now treated as a valid include directive:

#
#line 1
include
#line 1
"header.h"

This won't be the case after this change because the line directives are kept in the raw tokens, but I think that's alright because I don't think this is inteded to begin with.