Remove some debugging code inadverently left in __fish_complete_cd.fish
Make io_data_t::fd const

In exec(), pipe_{write,read} no longer get reused.
Make io_fd_t members const, make close_fd bool
Make io_file_t members const
In exec(), only add and remove pipe_{read,write} when necessary
exec(): Fix a stupid crash. Remove commented debug code that became invalidated.
Clean up env_var_table_t. Switch from storing var_uni_entry_t* to var_uni_entry_t. Various other cleanups.
Clean up export_func
Fixed broken export_func

Fix for https://github.com/fish-shell/fish-shell/issues/573
Fix to look up fish_pager in __fish_bin_dir instead of by using PATH, in preparation for making fish no longer need to modify PATH
Add function for fish_indent so that it does not need to be in PATH, in preparation for making fish no longer need to set PATH
First stab at builtin set_color. Moved set_color.cpp to builtin_set_color.cpp and taught fish about it.
Remove set_color from Makefile. Fix issue where builtin_set_color would mix output modes up
bulitin_set_color.cpp -> builtin_set_color.cpp
Remove set_color.cpp from Xcode project
Teach set_color to call setupterm so it doesn't crash when run non-interactively
Teach fish how to clean up installed versions of set_color
First round of fixes based on cppcheck
https://github.com/fish-shell/fish-shell/issues/575
Eliminate next pointer from connection_t, turn connections into a std::list
Migrate connection_t from storing a huge buffer to a std::vector