Remove struct keyword in range-based for loop

Remove struct keyword in range-based for loop

Fix this with  gcc 6.3.0:

/home/simark/src/binutils-gdb/gdb/symfile.c: In function 'void set_objfile_default_section_offset(objfile*, const section_addr_info&, CORE_ADDR)':
/home/simark/src/binutils-gdb/gdb/symfile.c:2114:14: error: types may not be defined in a for-range-declaration [-Werror]
   for (const struct other_sections *objf_sect : objf_addrs_sorted)
              ^~~~~~
gdb/ChangeLog:

	* symfile.c (set_objfile_default_section_offset): Remove struct
	keyword.