Implement the fprintf optimization which converts calls like this:

  fprintf(F,"hello") -> fwrite("hello",strlen("hello"),1,F)
  fprintf(F,"%s","hello") -> fwrite("hello",strlen("hello"),1,F)
  fprintf(F,"%c",'x') -> fputc('c',F)

This optimization fires severals times in llvm-test:

313 MultiSource/Applications/Burg
302 MultiSource/Benchmarks/Prolangs-C/TimberWolfMC
189 MultiSource/Benchmarks/Prolangs-C/mybison
175 MultiSource/Benchmarks/Prolangs-C/football
130 MultiSource/Benchmarks/Prolangs-C/unix-tbl

llvm-svn: 21657