Add _buf() functions to bypass static string buffers

We have a number of static buffers in use in libosmo*.  This means
the related functions are not usable in a thread-safe way.  While
we so far don't have many multi-threaded programs in the osmocom
universe, the static buffers also prevent us from calling the same
e.g. string-ify function twice within a single printf() call.

Let's make sure there's an alternative function in all those cases,
where the user can pass in a caller-allocated buffer + size, and make
the 'classic' function with the static buffer a wrapper around that
_buf() variant.

Change-Id: Ibf85f79e93244f53b2684ff6f1095c5b41203e05
diff --git a/include/osmocom/sim/sim.h b/include/osmocom/sim/sim.h
index 680cad1..0490dcd 100644
--- a/include/osmocom/sim/sim.h
+++ b/include/osmocom/sim/sim.h
@@ -296,6 +296,7 @@
 					uint16_t sw_in);
 
 struct osim_card_hdl;
+char *osim_print_sw_buf(char *buf, size_t buf_len, const struct osim_card_hdl *ch, uint16_t sw_in);
 char *osim_print_sw(const struct osim_card_hdl *ch, uint16_t sw_in);
 
 extern const struct tlv_definition ts102221_fcp_tlv_def;