Move the exports around to make everything clearer

src/lib/builtins/functions.rs

src/lib/builtins/job_control.rs

src/lib/builtins/man_pages.rs

src/lib/builtins/mod.rs

src/lib/builtins/source.rs

src/lib/builtins/variables.rs

src/lib/lib.rs

src/lib/parser/mod.rs

src/lib/parser/shell_expand/mod.rs

src/lib/parser/statement/mod.rs

src/lib/parser/statement/parse.rs

src/lib/shell/assignments.rs

src/lib/shell/binary/mod.rs

src/lib/shell/flow.rs

src/lib/shell/flow_control.rs

src/lib/shell/fork_function.rs

src/lib/shell/mod.rs

src/lib/shell/pipe_exec/fork.rs

src/lib/shell/pipe_exec/job_control.rs

src/lib/shell/pipe_exec/mod.rs