jit: check for void types [PR 95296]

jit: check for void types [PR 95296]

PR jit/95296 reports an ICE when using libgccjit to create a local of void
type.

This patch adds checking to various API entrypoints in libgccjit.c so that
they fail gracefully with an error if the client code attempts to create
various kinds of rvalues or types involving void types.
The patch documents these and various pre-existing restrictions on types
in the API.

gcc/jit/ChangeLog:
	PR jit/95296
	* docs/topics/expressions.rst (Unary Operations): Document that
	result_type of gcc_jit_context_new_unary_op must be a numeric type.
	(Binary Operations): Likewise for gcc_jit_context_new_binary_op.
	(Global variables): Document that "type" of
	gcc_jit_context_new_global must be non-`void`.
	* docs/topics/function-pointers.rst
	(gcc_jit_context_new_function_ptr_type): Document that the
	param_types must be non-void, but that return_type may be.
	* docs/topics/functions.rst (Params): Document that
	gcc_jit_context_new_param's type must be non-void.
	(Functions): Likewise for gcc_jit_function_new_local.
	* docs/topics/types.rst (gcc_jit_context_new_array_type): Document
	that the type must be non-void.
	(gcc_jit_context_new_field): Likewise.
	* docs/_build/texinfo/Makefile: Regenerate.
	* docs/_build/texinfo/libgccjit.texi: Regenerate.
	* libgccjit.c (gcc_jit_context_new_array_type): Fail if
	element_type is void.
	(gcc_jit_context_new_field): Likewise for "type".
	(gcc_jit_context_new_function_ptr_type): Likewise for each
	element of param_types.
	(gcc_jit_context_new_param): Likewise for "type".
	(gcc_jit_context_new_global): Likewise.
	(gcc_jit_function_new_local): Likewise.
	(gcc_jit_type_get_aligned): Likewise.

gcc/testsuite/ChangeLog:
	PR jit/95296
	* jit.dg/test-error-gcc_jit_context_new_global-void-type.c: New
	test.
	* jit.dg/test-error-gcc_jit_function_new_local-void-type.c: New
	test.
	* jit.dg/test-fuzzer.c (fuzzer_init): Allow for make_random_type
	to return NULL.
	(get_random_type): Allow for elements in f->types to be NULL.