Require libcurl as a system dependency

This purges libcurl from our tree and requires it to be present on the
system for building and running FreeSWITCH.

FS-353

libs/.gitignore

@@ -82,48 +82,6 @@ opal
 /broadvoice/tests/regression_tests.sh
 /celt-*/
 /Communicator_semi_40.cd_semi_6000/
-/curl/curl-config
-/curl/include/curl/Makefile
-/curl/include/curl/Makefile.in
-/curl/include/Makefile
-/curl/include/Makefile.in
-/curl/lib/config.h
-/curl/lib/Makefile
-/curl/lib/Makefile.in
-/curl/lib/stamp-h1
-/curl/Makefile
-/curl/Makefile.in
-/curl/packages/AIX/Makefile
-/curl/packages/AIX/Makefile.in
-/curl/packages/AIX/RPM/curl.spec
-/curl/packages/AIX/RPM/Makefile
-/curl/packages/AIX/RPM/Makefile.in
-/curl/packages/DOS/Makefile
-/curl/packages/DOS/Makefile.in
-/curl/packages/EPM/curl.list
-/curl/packages/EPM/Makefile
-/curl/packages/EPM/Makefile.in
-/curl/packages/Linux/Makefile
-/curl/packages/Linux/Makefile.in
-/curl/packages/Linux/RPM/curl.spec
-/curl/packages/Linux/RPM/curl-ssl.spec
-/curl/packages/Linux/RPM/Makefile
-/curl/packages/Linux/RPM/Makefile.in
-/curl/packages/Makefile
-/curl/packages/Makefile.in
-/curl/packages/Solaris/Makefile
-/curl/packages/Solaris/Makefile.in
-/curl/packages/vms/Makefile
-/curl/packages/vms/Makefile.in
-/curl/packages/Win32/cygwin/Makefile
-/curl/packages/Win32/cygwin/Makefile.in
-/curl/packages/Win32/Makefile
-/curl/packages/Win32/Makefile.in
-/curl/src/config.h
-/curl/src/Makefile
-/curl/src/Makefile.in
-/curl/src/stamp-h2
-/curl-*/
 /esl/Debug/
 /esl/Release/
 /flite-*/
@@ -912,7 +870,6 @@ opal
 !/apr-util/xml/expat/conftools/config.sub
 !/apr-util/xml/expat/conftools/install-sh
 !/apr-util/xml/expat/conftools/missing
-!/curl/src/config.h.in
 !/iksemel/ltmain.sh
 !/ldns/drill/config.h.in
 !/ldns/drill/configure
@@ -947,7 +904,6 @@ opal
 !/yaml/config/missing
 !/yaml/configure
 broadvoice/config/compile
-curl/compile
 ilbc/config/compile
 libedit/compile
 libg722_1/config/compile