gcov: Use system IO buffering

gcov: Use system IO buffering

gcc/ChangeLog:

	* gcov-io.c (gcov_write_block): Remove.
	(gcov_write_words): Likewise.
	(gcov_read_words): Re-implement using gcov_read_bytes.
	(gcov_allocate): Remove.
	(GCOV_BLOCK_SIZE): Likewise.
	(struct gcov_var): Remove most of the fields.
	(gcov_position): Implement with ftell.
	(gcov_rewrite): Remove setting of start and offset fields.
	(from_file): Re-format.
	(gcov_open): Remove setbuf call. It should not be needed.
	(gcov_close): Remove internal buffer handling.
	(gcov_magic): Use __builtin_bswap32.
	(gcov_write_counter): Use directly gcov_write_unsigned.
	(gcov_write_string): Use direct fwrite and do not round
	to 4 bytes.
	(gcov_seek): Use directly fseek.
	(gcov_write_tag): Use gcov_write_unsigned directly.
	(gcov_write_length): Likewise.
	(gcov_write_tag_length): Likewise.
	(gcov_read_bytes): Use directly fread.
	(gcov_read_unsigned): Use gcov_read_words.
	(gcov_read_counter): Likewise.
	(gcov_read_string): Use gcov_read_bytes.
	* gcov-io.h (GCOV_WORD_SIZE): Adjust to reflect
	that size is not in bytes, but words (4B).
	(GCOV_TAG_FUNCTION_LENGTH): Likewise.
	(GCOV_TAG_ARCS_LENGTH): Likewise.
	(GCOV_TAG_ARCS_NUM): Likewise.
	(GCOV_TAG_COUNTER_LENGTH): Likewise.
	(GCOV_TAG_COUNTER_NUM): Likewise.
	(GCOV_TAG_SUMMARY_LENGTH): Likewise.

libgcc/ChangeLog:

	* libgcov-driver.c: Fix GNU coding style.