[commit] Delete MIPS only DEPRECATED_IGNORE_HELPER_CALLER

[Andrew Cagney]

This is was added as a hack for mips16 floating-point.  Given that 
MIPS16 backtraces are pretty much AWAL, the loss of this hack is the 
least of the MIPS16 problems.  If anyone is interested in renovating the 
MIPS16 I'm all ears.

committed,
Andrew