[tlbuild] kpathsea/line.c using getc_unlocked

[Akira Kakuto]

Hi Karl,

> We do not attempt to use the functions on Windows; should be no change
> there.  There is no speedup on my CentOS 5 system, but no harm either.

I have tested elapsed time on Windows by
kpsewhich -var-value TEXMFLOCAL.

(1)
If I use _fgetc_nolock() in win32_getc with unsafe
#define FLOCKFILE(x)
#define FUNLOCKFILE(x)
newtime / oldtime = about 0.66

(2)
If I use _fgetc_nolock() in win32_getc with
#define FLOCKFILE(x) \
LockFile((HANDLE)_get_osfhandle(fileno(f)),0,0,0xFFFFFFFF,0xFFFFFFFF)
#define FUNLOCKFILE(x) \
UnlockFile((HANDLE)_get_osfhandle(fileno(f)),0,0,0xFFFFFFFF,0xFFFFFFFF)
newtime / oldtime = about 1.15

Therefore I'll leave the old method on Windows.

Thanks,
Akira