move a bunch more integer sizing out of target-specific code into

target indep code.  

Note that this changes functionality on PIC16: it defines __INT_MAX__
correctly for it, and it changes sizeof(long) to 16-bits (to match
the size of pointer).


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@57132 91177308-0d34-0410-b5e6-96231b3b80d8