Tighten .gitignore rules not to catch all the unittest source files
Create a unittest_bdiff umbrella executable for all bdiff tests
Reflow a long line
Add block_free (it looked oddly asymmetrical without it)
Added simple block tests
Add multiple differing blocks test
Merge branch 'block_tests'

Conflicts:
	tests/unittest_hash_counting_table.c [foolswood made functions static,
        ch3pjw had renamed variable]