DOC: update few references to the linux* targets and change them to linux-glibc

The INSTALL guide, the Lua doc and the Prometheus exporter's README all
used to reference "linux2628", "linux26" or even "linux". These were all
updated to consistently reflect "linux-glibc" instead. The default options
were updated there as well so that it should build cleanly on most distros.
3 files changed