Change some arguments to gdb::string_view instead of name+len

Change some arguments to gdb::string_view instead of name+len

Just some code cleanup. This change has a few benefits:
- Shorter argument list in the functions
- If the caller needs to calculate the string, they no longer
  need to explicitly call strlen
- It is easy to pass std::string to this (done in one place
  currently)

This also updates a couple of places that were passing 0/1 to
a bool parameter.

gdb/ChangeLog:

2019-10-29  Christian Biesinger  <cbiesinger@google.com>

	* coffread.c (record_minimal_symbol): Update.
	(process_coff_symbol): Update.
	* dbxread.c (read_dbx_symtab): Update.
	* dwarf2read.c (add_partial_symbol): Update.
	(fixup_go_packaging): Update.
	(load_partial_dies): Update.
	(new_symbol): Update.
	* elfread.c (record_minimal_symbol): Change signature to use
	gdb::string_view instead of name+len.
	(elf_symtab_read): Update.
	(elf_rel_plt_read): Update.
	* mdebugread.c (parse_partial_symbols): Update.
	(handle_psymbol_enumerators): Update.
	(new_symbol): Update.
	* minsyms.c (minimal_symbol_reader::record_full): Change signature
	to use gdb::string_view instead of name+len.
	* minsyms.h (class minimal_symbol_reader) <record_full>: Likewise.
	* psympriv.h (add_psymbol_to_list): Likewise.
	* psymtab.c (add_psymbol_to_bcache): Likewise.
	(add_psymbol_to_list): Likewise.
	* stabsread.c (define_symbol): Update.
	* symtab.c (symbol_set_names): Change signature to use gdb::string_view.
	* symtab.h (SYMBOL_SET_NAMES): Likewise.
	(symbol_set_names): Likewise.
	* xcoffread.c (scan_xcoff_symtab): Update.

Change-Id: I2675c6865e0368f9c755a1081088a53aa54dda4c