Improved BitOps.h.
Improved BitOps.h.

 * __fls has been renamed to find_last_bit_set
 * the x86 assembly implementation of find_last_bit_set is not selected
   by default
 * the generic implementation of find_last_bit_set supports 64bit
 * __builtin_clzl can be used to implement find_last_bit_set


rezhajulio/mitlm,tectronics/mitlm,mitlm/mitlm,mitlm/mitlm,raheelqader/mitlm,raheelqader/mitlm,jbeard4/mitlm,jbeard4/mitlm,andrewphamvn/mitlm,tectronics/mitlm,eddieantonio/mitlm,rezhajulio/mitlm,emawind84/mitlm,jiaxibei2008/mitlm,emawind84/mitlm,askender/mitlm,tectronics/mitlm,mitlm/mitlm,jiaxibei2008/mitlm,askender/mitlm,jiaxibei2008/mitlm,askender/mitlm,zhoususheng/mitlm,jbeard4/mitlm,raheelqader/mitlm,zhoususheng/mitlm,andrewphamvn/mitlm,andrewphamvn/mitlm,eddieantonio/mitlm,eddieantonio/mitlm,emawind84/mitlm,zhoususheng/mitlm,rezhajulio/mitlm