Use static and const where appropriate
Ignore generated autotools files

Anything which can be generated by autoreconf shouldn't be checked into
the repository.
Temporary commit before a pull.
Merge branch 'copyedit' of https://github.com/gim/Duplicates
static and const in C file
Altered duplicates to not consider files with unique sizes. Reduced
processing time by ~ 33%.
Also to push up a pull that removed a heap of autotools work files.