Patch installed: convert scan.h & system.h to ISO C

[Zack Weinberg]

"Kaveh R. Ghazi" <ghazi@caip.rutgers.edu> writes:

> Bootstrapped on sparc-sun-solaris2.7, installed as "obvious".

This raises the interesting question of whether we should expect a C90
_library_ from the host system.  If we do, then for instance we can
assume the existence of stdlib.h and string.h; we need not bother
including strings.h nor memory.h; we need not check in configure for
any C90 specified library function, nor provide fallback prototypes.

As far as I know we haven't decided on a definitive answer to this
question.

zw