bug#26490: 25.1; package-buffer-info is incorrectly case-insensitive

[Steve Purcell]

I’m going to bind case-fold-search to nil in my case anyway, but I don’t think 
you want a situation in which the case of the first and last lines differ, 
simply for the sake of consistency: that’s all that this patch ensures, and 
it’s orthogonal to filesystem case-sensitivity.

(Further, in package-lint, the intention is to check that the filenames on 
those lines exactly match the elisp buffer's filename, if any, and the name of 
the provided feature. Those comparisons should always be case-sensitive, I 
would think, because the elisp file could be taken from a local 
case-insensitive FS to a case-sensitive FS, and mismatches would presumably 
cause issues.)