ims_isc: fix compiler warnings

* inline functions were not defined at mark.h
  so the compiler was ignoring the inline directive

> In file included from mod.c:49:0:
> mark.h:78:12: warning: inline function 'isc_mark_write_route' declared but never defined
>  inline int isc_mark_write_route(struct sip_msg *msg,str *as,str *iscmark);
>             ^~~~~~~~~~~~~~~~~~~~
> mark.h:76:12: warning: inline function 'isc_mark_drop_route' declared but never defined
>  inline int isc_mark_drop_route(struct sip_msg *msg);
>             ^~~~~~~~~~~~~~~~~~~
> CC (gcc) [M ims_isc.so]		third_party_reg.o
> In file included from third_party_reg.h:52:0,
>                  from third_party_reg.c:46:
> mark.h:78:12: warning: inline function 'isc_mark_write_route' declared but never defined
>  inline int isc_mark_write_route(struct sip_msg *msg,str *as,str *iscmark);
>             ^~~~~~~~~~~~~~~~~~~~
> mark.h:76:12: warning: inline function 'isc_mark_drop_route' declared but never defined
>  inline int isc_mark_drop_route(struct sip_msg *msg);
>             ^~~~~~~~~~~~~~~~~~~
> CC (gcc) [M ims_isc.so]		isc.o
> In file included from isc.h:54:0,
>                  from isc.c:47:
> mark.h:78:12: warning: inline function 'isc_mark_write_route' declared but never defined
>  inline int isc_mark_write_route(struct sip_msg *msg,str *as,str *iscmark);
>             ^~~~~~~~~~~~~~~~~~~~
> mark.h:76:12: warning: inline function 'isc_mark_drop_route' declared but never defined
>  inline int isc_mark_drop_route(struct sip_msg *msg);
>             ^~~~~~~~~~~~~~~~~~~

src/modules/ims_isc/mark.c

@@ -197,7 +197,7 @@ int base16_to_bin(char *from, int len, char *to) {
  *	@param msg - SIP mesage to mark
  *	@returns 1 on success
  */
-inline int isc_mark_drop_route(struct sip_msg *msg) {
+int isc_mark_drop_route(struct sip_msg *msg) {
 	struct lump* lmp, *tmp;
 
 	parse_headers(msg, HDR_EOH_F, 0);
@@ -273,7 +273,7 @@ int isc_mark_set(struct sip_msg *msg, isc_match *match, isc_mark *mark) {
  *	@param iscmark - the mark to write
  *	@returns 1 on success, else 0
  */
-inline int isc_mark_write_route(struct sip_msg *msg, str *as, str *iscmark) {
+int isc_mark_write_route(struct sip_msg *msg, str *as, str *iscmark) {
 	struct hdr_field *first;
 	struct lump* anchor;
 	str route;

src/modules/ims_isc/mark.h

@@ -73,9 +73,9 @@ typedef struct _isc_mark{
 int isc_mark_get_from_msg(struct sip_msg *msg,isc_mark *mark);
 void isc_mark_get(str x,isc_mark *mark);
 int base16_to_bin(char *from,int len, char *to);
-inline int isc_mark_drop_route(struct sip_msg *msg);
+int isc_mark_drop_route(struct sip_msg *msg);
 int isc_mark_set(struct sip_msg *msg, isc_match *match, isc_mark *mark);
-inline int isc_mark_write_route(struct sip_msg *msg,str *as,str *iscmark);
+int isc_mark_write_route(struct sip_msg *msg,str *as,str *iscmark);
 int isc_mark_write_psu(struct sip_msg *msg, isc_mark *mark);
 int bin_to_base16(char *from,int len, char *to);