Untag for development
Fix an overzealous warning on 32-bit systems
Suppress some warnings that only seem to appear on Fedora

Using gcc 4.8 and 2.17 works fine on Debian, but not Fedora.

I'm planning on a better fix eventually, once I have distinct types
for integers of a specified endianness.
Don't break gcc < 4.8 with warnings on
Move contents of make.defs where they belong
Add gcc 4.8 to travis spec
remove some #warning pragma