expand_symtab_containing_pc: Renamed from find_pc_sect_symtab_via_partial.

expand_symtab_containing_pc: Renamed from find_pc_sect_symtab_via_partial.

This patch just renames one function.
Its only caller is in stack.c where we're printing a backtrace
with non-zero info_verbose and we want to make sure all the needed
symtabs are expanded before printing the backtrace
so that debug symbol reading messages don't pollute the backtrace.

I think the new name of the function makes clearer to the reader
what is going on.

gdb/ChangeLog:

	* symtab.c (expand_symtab_containing_pc): Renamed from
	find_pc_sect_symtab_via_partial.  All callers updated.