Support hexadecimal numbers in lexer.
Support hexadecimal numbers in lexer.

diku-dk/futhark,ihc/futhark,mrakgr/futhark,CulpaBS/wbBach,diku-dk/futhark,mrakgr/futhark,ihc/futhark,HIPERFIT/futhark,mrakgr/futhark,ihc/futhark,HIPERFIT/futhark,diku-dk/futhark,diku-dk/futhark,HIPERFIT/futhark,diku-dk/futhark