Missing includes; required at least for compiling against musl.

diff --git a/proc/readproc.c.orig b/proc/readproc.c
index 4fad11d..c5b1869 100644
--- a/proc/readproc.c.orig
+++ b/proc/readproc.c
@@ -26,6 +26,7 @@
 #include <sys/dir.h>
 #include <sys/types.h>
 #include <sys/stat.h>
+#include <limits.h>

 // sometimes it's easier to do this manually, w/o gcc helping
 #ifdef PROF