PR jit/66783: improve error messages

PR jit/66783: improve error messages

gcc/jit/ChangeLog:
	PR jit/66783
	* libgccjit.c (gcc_jit_context_new_field): Show name of field in
	"unknown size" error message.
	(gcc_jit_struct_set_fields): Show name of struct in error message.
	(gcc_jit_context_new_global): Show name of global in
	"unknown size" error message.
	(gcc_jit_function_new_local): Likewise for local.

gcc/testsuite/ChangeLog:
	PR jit/66783
	* jit.dg/test-error-gcc_jit_context_new_field-opaque-struct.c
	(verify_code): Update expected error message.
	* jit.dg/test-error-gcc_jit_context_new_global-opaque-struct.c
	(verify_code): Likewise.
	* jit.dg/test-error-gcc_jit_function_new_local-opaque-struct.c
	(verify_code): Likewise.

From-SVN: r225557