Changes for a `m88k-motorola-sysv3'

[Jim Wilson]

	Will checking __sysV88__ work?  I looked in m88k/sysv3.h and it
	only defines sysV88, not __sysV88__, in CPP_PREDEFINES. 

If foo is in CPP_PREDEFINES, then __foo__ will always be defined.

If foo is in CPP_PREDEFINES, then foo will be defined only if -pedantic (or
perhaps -ansi?) is not used.

In addition, there are a few other rules that apply to interpretation of
CPP_PREDEFINES.

Jim