Line/column number calculation regression

[Xenomega]

Recent adoption of crytic-compile in slither have required some code paths to be changed. A regression can be observed in source mapping line/column calculations due to CR, LF, and CRLF line endings, as described in #194 .

The problematic code can be found here:

slither/slither/slither.py

Line 68 in 04c147f

with open(path) as f:

The same solution described in the previous PR should be taken for all source file reading operations: retain format and line endings.

This issue currently will cause incorrect line/column number calculations in files with CRLF line endings.