configure: Add version string to pkg-config file

Use version plus revision: "Version: 1.13.8 rev.1041"
If revision is 0 (= if the .git dir is missing) use only version: "Version: 1.13.8"
Makefile: No need to make shared libs executable on Linux

>Shared libraries should not be installed executable, since the dynamic linker does not require this and trying to execute a shared library usually results in a core dump.

https://www.debian.org/doc/debian-policy/ch-sharedlibs.html#s-sharedlibs-runtime
configure: Update the URL within the pkg-config file.