Bug#863794: freemat: please re-enable LLVM support

[Graham Inggs]

How to verify that JIT is functioning correctly.

Check whether JIT is enabled:

--> jitcontrol
ans =
on

Enable it if needed:

--> jitcontrol('on')

Run something that can be JIT compiled:

--> A=0; for j=1:1000000; A=A+j; end

Debug window in bottom-left should show 'Block JIT compiled at line 1 of 
"docli"', or similar.  If freemat was started from a terminal, you 
should see CLANG output, and no errors indicated.

Running the same commands subsequent times should be faster.

The value of the 'jitstat' variable should increment after every run.

--> jitstat
ans =
  0

JIT tests from the freemat test suite can be run as follows:

--> wrap_jit_test('tjit1',0,true)
Speedup base 1.293000 target 0.000000 up 1.286000
Jit succeeded 0
Issame 1

Tests from 'tjit1' to 'tjit27' are available.
The line 'Jit succeeded 0' above indicates that 'jitstat' did not 
increment and JIT was not successful.