Remove OS, compiler version, date, and time from version string

[ryandesign]

agrep -V prints this on macOS:

AGREP 3.41.5/TG for NATIVE LINUX compiled with GCC Clang 17.0.5 (Nov 25 2023 18:24:29). Manber/Wu/Gries et al.

See:

https://github.com/Wikinaut/agrep/blob/b7d180fe73636740f694ec60c1ffab52b06e7150/version.h#L73

Please remove the OS name from this line since it is obviously fictitious on operating systems like macOS that you didn't explicitly consider and is not necessary since everybody already knows what operating system they're using.

Please remove "GCC" and the compiler version since it is confusing when the compiler that was used is not GCC and nobody cares what compiler or version a program was compiled with.

Please remove the compilation date and time since that renders your build non-reproducible and nobody cares when a program was compiled.