Omit frame pointer save/restore for functions that don't need it
Generate debug .file list separately from .loc

Note this is currently output too late in the generated assembly.
Section changes are needed for this.
Ensure the debug filelist is output first in the assembly

This should be done more elegantly when proper section support (e.g.
__attribute__((section("...")))) is added.
Generate prologue/epilogue for non-leaf functions
Test fixes for omit-frame-pointer

Callee-save only cares that the registers are saved, not where to.
The rest just don't generate the prologue label any more, or need
to force no-omit-frame-pointer.
TODO: debug info for (unused) stack vars