regs: Handle HUP signals

Enable capturing and handling a HUP signal to reload configuration data.

Tested:
    Handler function called upon receiving a SIGHUP

Signed-off-by: Matthew Barth <msbarth@us.ibm.com>
Change-Id: I41d136ede5f2a4c0bf595ee58993a4408f153013
diff --git a/meson.build b/meson.build
index 92c1450..1827472 100644
--- a/meson.build
+++ b/meson.build
@@ -38,6 +38,7 @@
 sdbuspp = find_program('sdbus++')
 sdeventplus = dependency('sdeventplus')
 pthread = dependency('threads')
+stdplus = dependency('stdplus')
 
 systemd = dependency('systemd')
 servicedir = systemd.get_pkgconfig_variable('systemdsystemunitdir')