add lowercase test for BSD, add check for sendmail, don't check for libdl, add check for backtrace

configure.ac

@@ -26,6 +26,12 @@ case $host_os in
    *BSD*)
         # Do something specific for BSD
 		HOST_OS='BSD'
+		AC_DEFINE(BSD,1,"This is a BSD system")
+        ;;
+   *bsd*)
+        # Do something specific for BSD
+		HOST_OS='BSD'
+		AC_DEFINE(BSD,1,"This is a BSD system")
         ;;
     *)
         #Default Case
@@ -315,7 +321,8 @@ AC_FUNC_STRTOD
 AC_FUNC_VPRINTF
 AC_CHECK_FUNCS([gethostbyname gethostname gettimeofday memmove memset mkdir munmap posix_memalign putenv select sendfile socket sqrt strcasecmp strchr strcspn strerror strncasecmp strrchr strspn strstr strtol strtoull])
 AC_CHECK_FUNCS([syscall sleep usleep ioctl ioctlsocket sigaction])
-
+# this is required for freebsd to compile
+AC_CHECK_SENDFILE
 # Other programs
 AC_CHECK_PROG(OPT_FFMPEG,ffmpeg,yes,no)
 AC_PATH_PROG(PATH_FFMPEG,ffmpeg)
@@ -330,7 +337,10 @@ AC_CHECK_LIB(rt,clock_gettime,,AC_MSG_ERROR(zm requires librt))
 AC_SEARCH_LIBS(mysql_init,[mysqlclient mariadbclient],,AC_MSG_ERROR(zm requires libmysqlclient.a or libmariadbclient.a))
 AC_CHECK_LIB(jpeg,jpeg_start_compress,,AC_MSG_ERROR(zm requires libjpeg.a))
 AC_CHECK_LIB(pthread,pthread_create,,AC_MSG_ERROR(zm requires libpthread.a))
+if test "$BSD" == "0"; then
 AC_CHECK_LIB(dl,dlsym,,AC_MSG_ERROR(zm requires libdl.a))
+fi
+AC_CHECK_LIB(execinfo,backtrace, , AC_MSG_ERROR([unable to find the backtrace() function]))
 if test "$ZM_SSL_LIB" == "openssl"; then
 AC_CHECK_HEADERS(openssl/md5.h,,AC_MSG_WARN(zm requires openssl/md5.h header to be installed for openssl),)
 AC_CHECK_LIB(crypto,MD5,,AC_MSG_WARN([libcrypto.a is required for authenticated streaming - use ZM_SSL_LIB option to select gnutls instead]))
@@ -470,32 +480,6 @@ fi
 AC_SUBST(PERL_MM_PARMS)
 AC_SUBST(EXTRA_PERL_LIB)
 
-#
-# Platform specific setup
-#
-#############################
-AC_CANONICAL_HOST
-# Check for which host we are on and setup a few things
-# specifically based on the host
-case $host_os in
-  darwin* )
-        # Do something specific for mac
-		HOST_OS='darwin'
-        ;;
-  linux*)
-        # Do something specific for linux
-		HOST_OS='linux'
-        ;;
-   *BSD*)
-        # Do something specific for BSD
-		HOST_OS='BSD'
-        ;;
-    *)
-        #Default Case
-        AC_MSG_ERROR([Your platform is not currently supported])
-        ;;
-esac
-
 AC_CONFIG_FILES([Makefile zm.conf zmconfgen.pl db/Makefile db/zm_create.sql misc/Makefile misc/apache.conf misc/logrotate.conf misc/syslog.conf misc/com.zoneminder.systemctl.policy misc/com.zoneminder.systemctl.rules onvif/Makefile onvif/scripts/Makefile scripts/Makefile scripts/zm scripts/zmaudit.pl scripts/zmcontrol.pl scripts/zmdc.pl scripts/zmfilter.pl scripts/zmpkg.pl scripts/zmtrack.pl scripts/zmcamtool.pl scripts/zmsystemctl.pl scripts/zmtrigger.pl scripts/zmupdate.pl scripts/zmvideo.pl scripts/zmwatch.pl scripts/zmx10.pl scripts/zmdbbackup scripts/zmdbrestore scripts/zmeventdump scripts/zmlogrotate.conf scripts/ZoneMinder/lib/ZoneMinder/Base.pm scripts/ZoneMinder/lib/ZoneMinder/Config.pm scripts/ZoneMinder/lib/ZoneMinder/Memory.pm scripts/ZoneMinder/lib/ZoneMinder/ConfigData.pm src/Makefile src/zm_config.h web/Makefile web/ajax/Makefile web/css/Makefile web/graphics/Makefile web/includes/Makefile web/includes/config.php web/js/Makefile web/lang/Makefile web/skins/Makefile web/skins/classic/Makefile web/skins/classic/ajax/Makefile web/skins/classic/css/Makefile web/skins/classic/css/classic/Makefile web/skins/classic/css/classic/views/Makefile web/skins/classic/css/flat/Makefile web/skins/classic/css/flat/views/Makefile web/skins/classic/graphics/Makefile web/skins/classic/includes/Makefile web/skins/classic/js/Makefile web/skins/classic/lang/Makefile web/skins/classic/views/Makefile web/skins/classic/views/js/Makefile web/skins/mobile/Makefile web/skins/mobile/ajax/Makefile web/skins/mobile/css/Makefile web/skins/mobile/graphics/Makefile web/skins/mobile/includes/Makefile web/skins/mobile/lang/Makefile web/skins/mobile/views/Makefile web/skins/mobile/views/css/Makefile web/tools/Makefile web/tools/mootools/Makefile web/views/Makefile web/skins/xml/Makefile web/skins/xml/views/Makefile web/skins/xml/includes/Makefile])
 
 # Create the definitions for compilation and defaults for the database