Enable dtrace probes on linux as they are compatible with systemtap

You can build php with dtrace probes enabled on linux if you have
systemtap with uprobes.

Author: dsp

acinclude.m4

@@ -2934,6 +2934,9 @@ dnl Add providerdesc.o into global objects when needed
   *solaris*)
     PHP_GLOBAL_OBJS="[$]PHP_GLOBAL_OBJS [$]ac_bdir[$]ac_provsrc.o"
     ;;
+  *linux*)
+    PHP_GLOBAL_OBJS="[$]PHP_GLOBAL_OBJS [$]ac_bdir[$]ac_provsrc.o"
+    ;;
   esac
 
 dnl DTrace objects