Linux abs() needs to be fabs(); a few other minor Linux tweaks.

git-svn-id: https://cvs.khronos.org/svn/repos/ogl/trunk/ecosystem/public/sdk/tools/glslang@22603 e7fa87d3-cd2b-0410-9028-fcbf551c1848

Test/runtests

@@ -7,5 +7,5 @@ while read t; do
     echo Running $t...
 	b=`basename $t`
     ./glslangValidator.exe -i $t > $TARGETDIR/$b.out
-    diff $BASEDIR/$b.out $TARGETDIR/$b.out
+    diff -b $BASEDIR/$b.out $TARGETDIR/$b.out
 done < testlist