libosmocore libusb integration

Osmocom applications typically use libosmocore select.[ch] event loop
code as their main event dispatch mechanism.  When they want to deal
with libusb in a non-blocking/asynchronous way, they need to integrate
libusb into that select().

The new libosmousb is doing exactly that: Providing a shared utility
library for Osmocom programs that wish to use libusb.  This is useful
for example in simtrace2 host utilitie as well as osmo-e1d.

Change-Id: I656a1a38cbb5b1f3a9145d2869d3b4d0adefcae3
Closes: OS#4299
diff --git a/libosmousb.pc.in b/libosmousb.pc.in
new file mode 100644
index 0000000..ce6d271
--- /dev/null
+++ b/libosmousb.pc.in
@@ -0,0 +1,11 @@
+prefix=@prefix@
+exec_prefix=@exec_prefix@
+libdir=@libdir@
+includedir=@includedir@
+
+Name: Osmocom libusb (USB) integration
+Description: C Utility Library
+Version: @VERSION@
+Libs: -L${libdir} @TALLOC_LIBS@ -losmousb -losmocore
+Cflags: -I${includedir}/
+