cpphash.c (_cpp_destroy_hashtable): Use ht_destroy.

cpphash.c (_cpp_destroy_hashtable): Use ht_destroy.

	* cpphash.c (_cpp_destroy_hashtable): Use ht_destroy.
	* cpphash.h (CPP_IN_SYSTEM_HEADER): Fix.
	(struct cpp_pool): New member first.
	* cppinit.c (append_include_chain): Plug memory leaks.
	* cpplib.c (cpp_register_pragma, cpp_register_pragma_space):
	Allocate pragma structures from the (aligned) macro pool to
	avoid leaking memory.
	* cpplex.c (_cpp_init_pool, _cpp_free_pool): Use pool->first
	so we don't leak memory.
	* hashtable.c (ht_destroy): New.
	* hashtable.h (ht_destroy): New.

From-SVN: r44794