resize_section_table cleanup

resize_section_table cleanup

	* exec.c (exec_close_1): Call clear_section_table instead of
	resize_section_table.
	(clear_section_table): New function.
	(resize_section_table): Make static.  Rename arg num_added to
	adjustment.
	* exec.h (clear_section_table): Declare.
	(resize_section_table): Delete.
	* progspace.c (release_program_space): Call clear_section_table
	instead of resize_section_table.