Fix regexp locations

[TadeasKucera]

In #124 we fix the locations of tokens of PlainString and HexString. We still need to do it for the Regexp class, and it's fellow classes like RegexpOr, RegexpGroup. The problem is that the Token class instances, that a particular regexp consists of are not created right in the tokenizer in parser_driver.cpp. The Token class instances in regexps are created in regexp classes constructors. Because of this, we cannot assign these tokens proper location within the parsed file. There are two possible ways to address this issue:

• Create the tokens in the tokenizer methods with proper locations and then distribute these tokens into new regexp classes constructors.

• Assign two locations - begin and end - to the regexp string after it is created. The locations of each token inside the regexp are not that important for us, and therefore it could be sufficient to only provide beginning and end of each regexp string. (Not necessary each of its tokens.)