Added fast math flag

1. Use -DHIP_FAST_MATH to make precise math functions compiled to fast math
2. Added double fast math functions for sqrt
3. Changed hipcc to parse -use_fast_math (not working)
4. Added passed tag to hipFloatMath test

Change-Id: I72884b2436b4efe61e9a9297346c1358fee38a2d

bin/hipcc

@@ -274,6 +274,11 @@ foreach $arg (@ARGV)
         $buildDeps = 1;
     }
 
+    if($arg eq '-use_fast_math') {
+        print "In fast Math";
+        $HIPCXXFLAGS .= " -DHIP_FAST_MATH ";
+    }
+
     if ($arg =~ m/^-/) {
         # options start with -