Try to detect if compiling with a 32bit or 64bit compiler.
Add system info (OS / CPUs/ RAM / Distribution (when on Linux)).
Remove qtaccessiblewidgets as QTPLUGIN.

MXE now ships Qt-5.4.0-rc which has accessibility built-in. All other
platforms did not have it enabled so far.
Guard against reading huge files.
#1057 Sysinfo for Mac OS X
Merge pull request #1062 from openscad/sysinfo

Report system information in the 'Library Info' dialog