dwarf2read.c: Some C++fycation, use std::vector, std::unique_ptr

dwarf2read.c: Some C++fycation, use std::vector, std::unique_ptr

This starts off as replacing a couple custom open coded vector
implementations in the file with std::vector, and then the rest falls
off of that.  I.e., use new/delete instead of XCNEW/xfree, add
ctors/dtors/initializers where appropriate.  And then use
std::unique_ptr instead of cleanups.  Some functions became methods,
and in a couple spots, some single-use callback functions that would
have to be tweaked anyway are converted to lambdas instead.

gdb/ChangeLog:
2017-04-04  Pedro Alves  <palves@redhat.com>

	* dwarf2read.c (struct file_entry): Add ctors, and initialize all
	fields.
	(line_header): Initialize all data fields.  Change type of
	standard_opcode_lengths to std::unique_ptr<unsigned char[]>.
	Change type of include_dirs to std::vector<const char *>.  Remove
	num_include_dirs, include_dirs_size.  Change type of file_names to
	std::vector<file_entry>.  Remove num_file_names, file_names_size.
	(line_header::line_header): New.
	(line_header::add_include_dir, line_header::add_file_name): New
	methods.
	(line_header::include_dir_at): Remove NULL check.
	(line_header::file_name_at): Add const overload.
	(line_header_up): New unique_ptr typedef.
	(dw2_get_file_names_reader): Use line_header_up.  Adjust to use
	std::vector.  Remove free_line_header call.
	(dwarf2_build_include_psymtabs): Use line_header_up.  Remove
	free_line_header call.
	(free_cu_line_header): Delete.
	(handle_DW_AT_stmt_list, handle_DW_AT_stmt_list)
	(setup_type_unit_groups): Use line_header_up instead of cleanups.
	Adjust to use std::vector.
	(free_line_header): Delete.
	(free_line_header_voidp): Use delete.
	(add_include_dir): Replace with ...
	(line_header::add_include_dir): ... this method.  Use std::vector.
	(add_file_name): Replace with ...
	(line_header::add_file_name): ... this method.  Use std::vector.
	(add_include_dir_stub): Delete.
	(read_formatted_entries): Remove memset.
	(dwarf_decode_line_header): Return a line_header_up instead of a
	raw pointer.  Remove cleanup handling.  Pass lambdas to
	read_formatted_entries.  Adjust to use line_header methods.
	(dwarf_decode_lines_1): Adjust to use line_header methods.
	(dwarf_decode_lines, file_file_name, file_full_name): Adjust to
	use std::vector.