compile: Rename struct type_map_instance::gcc_type field

compile: Rename struct type_map_instance::gcc_type field

Fixes:

  src/gdb/compile/compile-c-types.c:36:12: error: declaration of ‘gcc_type type_map_instance::gcc_type’ [-fpermissive]
     gcc_type gcc_type;
	      ^
  In file included from src/gdb/../include/gcc-c-interface.h:23:0,
		   from src/gdb/compile/compile-internal.h:21,
		   from src/gdb/compile/compile-c-types.c:23:
  src/gdb/../include/gcc-interface.h:32:28: error: changes meaning of ‘gcc_type’ from ‘typedef long long unsigned int gcc_type’ [-fpermissive]
   typedef unsigned long long gcc_type;
			      ^
  src/gdb/compile/compile-c-types.c: In function ‘gcc_type convert_qualified(compile_c_instance*, type*)’:
  src/gdb/compile/compile-c-types.c:310:19: error: invalid conversion from ‘int’ to ‘gcc_qualifiers’ [-fpermissive]
		quals);
		     ^

gdb/ChangeLog:
2015-10-29  Pedro Alves  <palves@redhat.com>

	* compile/compile-c-types.c (struct type_map_instance)
	<gcc_type>: Rename to gcc_type_handle.
	(insert_type, convert_type): Adjust.