changed: remove string.h from linux PlatformDefs

this strips 24kb off a shitload of compilation units. should speed
up compile slightly (no timings performed)
changed: remove fcntl.h from linux PlatformDefs

this strips 12kb off a shitload of compilation units. should
speed up compile slightly (no timings performed)
changed: remove fcntl.h from linux PlatformDefs

this strips 44kb off a shitload of compilation units. should
speed up compile slightly (no timings performed)
changed: remove unistd.h from linux PlatformDefs

this strips 44kb off a shitload of compilation units.
should speed up compile slightly (no timings performed)