Kernel: Move syscall implementations out of Process.cpp

This is something I've been meaning to do for a long time, and here we
finally go. This patch moves all sys$foo functions out of Process.cpp
and into files in Kernel/Syscalls/.

It's not exactly one syscall per file (although it could be, but I got
a bit tired of the repetitive work here..)

This makes hacking on individual syscalls a lot less painful since you
don't have to rebuild nearly as much code every time. I'm also hopeful
that this makes it easier to understand individual syscalls. :^)

Kernel/VM/Region.h

@@ -225,4 +225,17 @@ private:
     mutable OwnPtr<Bitmap> m_cow_map;
 };
 
+inline unsigned prot_to_region_access_flags(int prot)
+{
+    unsigned access = 0;
+    if (prot & PROT_READ)
+        access |= Region::Access::Read;
+    if (prot & PROT_WRITE)
+        access |= Region::Access::Write;
+    if (prot & PROT_EXEC)
+        access |= Region::Access::Execute;
+    return access;
+}
+
+
 }