Adds a link check in to the LLVM find script to make sure it can actually link against the library it finds.
Noticed this issue since I have a non-standard LLVM version built and installed.

Ubuntu 14.04 has miniupnpc 1.6.3
REGEX was failing because the string was empty, causing cmake to
error and not generate a Makefile.

This allows systems with older versions of miniupnpc to fall back
to the statically linked version in externals.

miniupnpc.h provides MINIUPNPC_API_VERSION since 1.7 and we require 1.7
or later, so there is no reason to have version detection code for older
versions.

Adds a cmake module to correctly discover OProfile and adjusts the
corresponding CMakeLists to make use of it. Additionally removes
linking against the bfd library when compiling with OProfile because
Dolphin does not use it.

Update mbed TLS (PolarSSL)

this enables support for that should the build system have that specific version installed, the miniupnpc bundled in the project is unchanged

For some dumb reason, llvm-config doesn't provide the flags to link
against the dynamic library copy of LLVM (as opposed to static), so the
script has to guess the library name.  However, in some installations
(such as mine), there is no dynamic copy, which caused Dolphin to fail
to link.  Change the script to do a link test.  If it fails, one option
would be to fall back on static linking, but I just have it fail to
detect LLVM, because statically linking Dolphin against LLVM is really
not a great idea - huge binary, long link time.