Link to POSIX recommendations in README is broken

[ilazaric]

pflag/README.md

Line 15 in b85eb9e

[1]: http://www.gnu.org/software/libc/manual/html_node/Argument-Syntax.html

Clicking it redirects me to https://sourceware.org/glibc/manual/

I believe it should be changed to: https://sourceware.org/glibc/manual/latest/html_node/Argument-Syntax.html

[tomasaschan]

Thanks for reporting!