This patch reworks how llvm targets set

and update ELF header e_flags.

Currently gathering information such as symbol, 
section and data is done by collecting it in an 
MCAssembler object. From MCAssembler and MCAsmLayout 
objects ELFObjectWriter::WriteObject() forms and 
streams out the ELF object file.

This patch just adds a few members to the MCAssember 
class to store and access the e_flag settings. It 
allows for runtime additions to the e_flag by 
assembler directives. The standalone assembler can 
get to MCAssembler from getParser().getStreamer().getAssembler().

This patch is the generic infrastructure and will be
followed by patches for ARM and Mips for their target 
specific use.

Contributer: Jack Carter
 
llvm-svn: 173882