add limits.h shim for defining PATH_MAX on HP-UX

include/compat/limits.h

@@ -0,0 +1,26 @@
+/*
+ * Public domain
+ * limits.h compatibility shim
+ */
+
+#ifndef LIBCRYPTOCOMPAT_LIMITS_H
+#define LIBCRYPTOCOMPAT_LIMITS_H
+
+#ifdef _MSC_VER
+#if _MSC_VER >= 1900
+#include <../ucrt/limits.h>
+#else
+#include <../include/limits.h>
+#endif
+#else
+#include_next <limits.h>
+#endif
+
+#ifdef __hpux
+#include <sys/param.h>
+#ifndef PATH_MAX
+#define PATH_MAX MAXPATHLEN
+#endif
+#endif
+
+#endif