Auto-generate Version_libclang_bindings module

[TravisCardwell]

This PR adds clangVersionCompileTime :: Text to the Clang.Version module. It is the full version string as reported by clang_getClangVersion at compile-time. This is done so that we can use clang_getClangVersion at run-time and compare the versions (as text, not parsed versions).

This works by using autoconf to link a C program that prints the version. This program is run, and the output is captured. The version string is then written into a Haskell module template, with double quotes escaped. The module is named Version_libclang_bindings to match the naming style of other autogen modules. It is exposed internally (in other-modules), and clangVersionCompileTime is re-exported by public module Clang.Version.

$ cabal repl
...
Configuring library for libclang-bindings-0.1.0...
...
checking libclang version... clang version 21.1.4
...
config.status: creating autogen/Version_libclang_bindings.hs
...
Ok, 30 modules loaded.
λ: import Clang.Version
λ: print clangVersionCompileTime
"clang version 21.1.4"
it :: ()

This has not been tested on Windows or macOS yet, but it should work.