Instrument multiple functions and count calls of user given "enter"
and "exit" functions.

> igprof -fmint FUNCTION1:LIBRARY1,FUNCTION2:LIBRARY2... (instruments
	functions that pass return value in %rax register. Max 10 functions)
> igprof -fmdouble FUNCTION1:LIBRARY1,FUNCTION2:LIBRARY2...(instruments
	functions that return value %XMM0 register.
All the functions increment the same counter.

> igprof --fenter-exit ENTERFUNCTION:LIBRARY EXITFUNCTION:LIBRARY
Counts calls to given functions. User can specify up to 10 enter functions and
10 exit functions.
Enter functions share one call counter and exit functions share another counter.

The x86 instruction length decoder has a new design. More supported instructions
added and the length lookup is now done trough opcode map tables.