add -u and -g command line args to set user and group.

properly handle portability for mlockall and setrlimit
Tested on linux, Freebsd, solaris, mac.
FSCORE-47

git-svn-id: http://svn.freeswitch.org/svn/freeswitch/trunk@6033 d0543943-73ff-0310-b7d9-9358b9ac24b2

src/include/switch_core.h

@@ -1413,6 +1413,18 @@ SWITCH_DECLARE(switch_status_t) switch_core_management_exec(char *relative_oid,
 */
 SWITCH_DECLARE(int32_t) set_high_priority(void);
 
+/*! 
+  \brief Change user and/or group of the running process
+  \long Several possible combinations:
+  - user only (group NULL): switch to user and his primary group (and supplementary groups, if supported)
+  - user and group: switch to user and specified group (only)
+  - group only (user NULL): switch group only
+  \param user name of the user to switch to (or NULL)
+  \param group name of the group to switch to (or NULL)
+  \return 0 on success, -1 otherwise
+*/
+SWITCH_DECLARE(int32_t) change_user_group(const char *user, const char *group);
+
 /*! 
   \brief Run endlessly until the system is shutdown
   \param bg divert console to the background