Fetching the TTY name of a process is extremely expensive on darwin and
the call to devname accounts for 95% of htop's CPU usage when there is
high process turnover (this is mostly due to devname calling lstat,
which is incredibly slow). This can make htop unresponsive.
To mitigate this only set the process TTY name if the it is being
actively displayed (PROCESS_FLAG_TTY), which by default it is not
on darwin.
Division by 100000.0 worked because `sysconf(_SC_CLK_TCK)` happened to be 100.
By unhardcoding:
1) It becomes more clear what this 100000.0 figure comes from.
2) It protects against bugs in the case `sysconf(_SC_CLK_TCK)` ever changes.
Use only one enum instead of a global and a platform specific one.
Drop Platform_numberOfFields global variable.
Set known size of Process_fields array
Reasoning:
- implementation was unsound -- broke down when I added a fairly
basic macro definition expanding to a struct initializer in a *.c
file.
- made it way too easy (e.g. via otherwise totally innocuous git
commands) to end up with timestamps such that it always ran
MakeHeader.py but never used its output, leading to overbuild noise
when running what should be a null 'make'.
- but mostly: it's just an awkward way of dealing with C code.
