fix Math::clog etc to not get generated if libm does not have

Author: mohawk2

lib/PDL/Math.pd

@@ -491,6 +491,7 @@ works with native-complex data.
 
 sub cequiv {
   my ($func, $ref) = @_;
+  return if !PDL::Core::Dev::got_complex_version($func, 1);
   pp_def("c$func",
       GenericTypes => $AF,
       Pars => 'i(); complex [o] o()',

t/math.t

@@ -5,6 +5,7 @@ use PDL::LiteF;
 use PDL::Math;
 use Test::PDL -atol => 0.01;
 use Config;
+require PDL::Core::Dev;
 
 is_pdl bessj0(0.5), pdl(0.9384), "bessj0";
 is_pdl bessj0(0), ldouble(1), "bessj0";
@@ -54,10 +55,10 @@ is_pdl erfi(erf(0.5)), pdl(0.5), "erfi (both ways)";
   is_pdl pdl('-2i')->csqrt, pdl('1-i');
 }
 
-is_pdl cacosh(-1), pdl('3.141592i');
-is_pdl clog(-1), pdl('3.141592i');
-is_pdl cacos(-2), pdl('3.141592-1.316957i');
-is_pdl casin(-2), pdl('-1.570796+1.316957i');
+is_pdl cacosh(-1), pdl('3.141592i') if PDL::Core::Dev::got_complex_version('acosh', 1);
+is_pdl clog(-1), pdl('3.141592i') if PDL::Core::Dev::got_complex_version('log', 1);
+is_pdl cacos(-2), pdl('3.141592-1.316957i') if PDL::Core::Dev::got_complex_version('acos', 1);
+is_pdl casin(-2), pdl('-1.570796+1.316957i') if PDL::Core::Dev::got_complex_version('asin', 1);
 
 {   # csqrt_up
   my $pi=4*atan2(1,1);