GitLab

	insists on defining SIGCHLD, even if it already has a definition.
	(file_p): Use the constant 4 instead of R_OK; empirically, the
	number is more portable than the symbol if you count the #include
	hair you have to go through to get R_OK defined.  Ffile_readable_p
	does this too.

	* xrdb.c (getuid): Declare this to return short.