misc: Move the bsc_parse_reg to libcommom and name it gsm_parse_reg

Move the regexp parsing code from the NAT to libcommon as it will
be used by the NAT and BSC code. This also adds the #include <regex.h>
include to gsm_data. This header should be split up.
diff --git a/openbsc/include/openbsc/gsm_data_shared.h b/openbsc/include/openbsc/gsm_data_shared.h
index 1dec0e4..a639a1c 100644
--- a/openbsc/include/openbsc/gsm_data_shared.h
+++ b/openbsc/include/openbsc/gsm_data_shared.h
@@ -1,6 +1,7 @@
 #ifndef _GSM_DATA_SHAREDH
 #define _GSM_DATA_SHAREDH
 
+#include <regex.h>
 #include <stdbool.h>
 #include <stdint.h>
 
@@ -588,4 +589,12 @@
 uint8_t gsm_ts2chan_nr(const struct gsm_bts_trx_ts *ts, uint8_t lchan_nr);
 uint8_t gsm_lchan2chan_nr(const struct gsm_lchan *lchan);
 
+/*
+ * help with parsing regexps
+ */
+int gsm_parse_reg(void *ctx, regex_t *reg, char **str,
+		int argc, const char **argv) __attribute__ ((warn_unused_result));
+
+
+
 #endif