Replace size_t with unsigned long.

size_t is not compatible type for `%lu`.
Makefile/tests: use return values to communicate errors
fish_tests.cpp: set return value if tests fail
configure/Makefile: remove unused variables and unneeded declarations
Fix for recent issue where random text might appear underlined.
Relax the requirement that we find a working 'doc' directory in order
for fish to be relocatable. Instead we only look for data and
configuration path
Merge remote-tracking branch 'upstream/master' into bind_mode
Merge branch 'bind_mode' of github.com:furunkel/fish-shell into bind_mode