libsysprof: add mountinfo helper

The goal of this helper is to simplify the process of parsing information
about mounts and the mountinfo for per-process maps. We should be able
to change sysprof-proc-source to use this and have better support for
getting the libraries within different mount namespaces.

src/libsysprof/meson.build

@@ -69,6 +69,7 @@ libsysprof_private_sources = [
   'sysprof-kallsyms.c',
   'sysprof-line-reader.c',
   'sysprof-map-lookaside.c',
+  'sysprof-mountinfo.c',
   'sysprof-polkit.c',
   'sysprof-symbol-map.c',
   ipc_service_src,