In rare occassions, it may happen that string table is allocated free
space preceeding symbol table. This is an error in the eyes of the `dyld`
dynamic loader and thus has to forbidden by the linker.
Fixes two scenarios where @boolToInt() calls were missing:
1. Boolean expression cast to different-size int (char, long, etc)
2. Boolean expression used as parameter for function with int argument
It turns out I was wrong and we can set the page size to the actual
page size used by the target architecture when dividing the binary
into chunks and calculating a hash of each chunk for embedding within
the adhoc code signature. This shaves of a considerable amount of bytes
since we divide the code signature section by at least 2x.
I've also unified the `write` interface of `CodeSignature` struct to
follow that used in every other bit of `MachO`; namely, the functions
now accept a writer instead of a buffer, therefore, there is no need
to manually track where to write each struct field anymore.
* move concurrency primitives that always operate on kernel threads to
the std.Thread namespace
* remove std.SpinLock. Nobody should use this in a non-freestanding
environment; the other primitives are always preferable. In
freestanding, it will be necessary to put custom spin logic in there,
so there are no use cases for a std lib version.
* move some std lib files to the top level fields convention
* add std.Thread.spinLoopHint
* add std.Thread.Condition
* add std.Thread.Semaphore
* new implementation of std.Thread.Mutex for Windows and non-pthreads Linux
* add std.Thread.RwLock
Implementations provided by @kprotty
