[analyzer] NumberObjectConversion: support more types, misc updates.

Support CFNumberRef and OSNumber objects, which may also be accidentally
converted to plain integers or booleans.

Enable explicit boolean casts by default in non-pedantic mode.

Improve handling for warnings inside macros.

Improve error messages.

Differential Revision: https://reviews.llvm.org/D25731

llvm-svn: 285533