[analyzer] Replace bug category magic strings with shared constants.

One small functionality change is to bring the sizeof-pointer checker in
line with the other checkers by making its category be "Logic error"
instead of just "Logic". There should be no other functionality changes.

Patch by Daniel Marjamäki!

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@191910 91177308-0d34-0410-b5e6-96231b3b80d8
Ignore -mieee-fp.

It looks like clang always produce code with the ieee comparisons, so it is
safe to ignore this flag (we still error on -mno-ieee-fp).

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@191912 91177308-0d34-0410-b5e6-96231b3b80d8