Use bool in normal_cmd().

Change signature of set_vcount_ca for consistency.
Use bool in do_mouse().

Change the signature of get_mouse_button() for consistency, and because
only do_mouse() uses it.
Use bool or int for local flag variables.

In do_pending_operator(), nv_zet(), nv_indent(), nv_g_cmd(), and more,
replace integer flags with bools when appropriate.

However, do keep the TRUEs and FALSEs of nv_cmds[].cmd_arg. It may store
values other than TRUE or FALSE, so it seems to make sense to use
integral constants.
Use bool in signatures of functions in normal.h.

Return bool from checkclearop, checkclearopq, add_to_showcmd,
find_decl, nv_screengo, get_visual_text, and unadjust_for_sel as these
functions all return either TRUE or FALSE or OK or FAIL, but not MAYBE.

Change to arguments toplevel of normal_cmd, check of
do_check_scrollbind, and locally and thisblock of finddecl, to bools as
they represent predicates.