Make host_address_to_string/gdb_print_host_address cast parameter to 'void *'

Fixes a set of errors like:

 ../../src/gdb/symfile-debug.c: In function ‘int debug_qf_map_symtabs_matching_filename(objfile*, const char*, const char*, int (*)(symtab*, void*), void*)’:
 ../../src/gdb/symfile-debug.c:137:39: error: invalid conversion from ‘int (*)(symtab*, void*)’ to ‘const void*’ [-fpermissive]
	host_address_to_string (callback),
					^

Note this has to work with data and function pointers.  In C++11 we
may perhaps do something a bit safer, but we're not there yet, and I
don't think it really matters.  For now just always do a simple
C-style cast in host_address_to_string itself.  No point in adding a
void * cast to each and every caller.

gdb/ChangeLog:
2015-10-27  Pedro Alves  <palves@redhat.com>

	* common/print-utils.c (host_address_to_string): Rename to ...
	(host_address_to_string_1): ... this.
	* common/print-utils.h (host_address_to_string): Reimplement as
	wrapper around host_address_to_string_1.
	* utils.c (gdb_print_host_address): Rename to ...
	(gdb_print_host_address_1): ... this.
	* utils.h (gdb_print_host_address): Reimplement as wrapper macro
	around	host_address_to_string_1.

gdb/common/print-utils.c

@@ -316,7 +316,7 @@ core_addr_to_string_nz (const CORE_ADDR addr)
 /* See print-utils.h.  */
 
 const char *
-host_address_to_string (const void *addr)
+host_address_to_string_1 (const void *addr)
 {
   char *str = get_cell ();