linux/hardware.rb: Add optimization flags

Closes #71
Add texinfo to base requirements

It will be required makeinfo by many formulae.
OSX (Xtools?) have it. So it's better to install texinfo by apt/yum.

Closes #73
Linuxbrew: Fix bug in parse_ldd_output

Closes #74
Linuxbrew: MacOS.version.to_sym returns :linux

Return :linux rather than :dunno
Linuxbrew: Fix MacOS.version.from_symbol

Return 'linux' rather than nil

Closes #76
Merge remote-tracking branch 'linux/linuxbrew' into feature/linux/linuxbrew
Merge branch 'feature/linux/linuxbrew' into develop