[analyzer] Don't flag strcpy of string literals into sufficiently large buffers.
In the security package, we have a simple syntactic check that warns about
strcpy() being insecure, due to potential buffer overflows.
Suppress that check's warning in the trivial situation when the source is an
immediate null-terminated string literal and the target is an immediate
sufficiently large buffer.
Patch by András Leitereg!
Differential Revision: https://reviews.llvm.org/D41384