unifdef.c : conflicting types for getline function 해결

From: Kyle McMartin <kyle@redhat.com>

Rawhide builds are currently failing to build unifdef.c, as the next
version of glibc changes the default _POSIX_C_SOURCE level, which
exposes getline() from <stdio.h>

scripts/unifdef.c:209: error: conflicting types for 'getline'
/usr/include/stdio.h:653: note: previous declaration of 'getline' was
here
make[2]: *** [scripts/unifdef] Error 1
make[1]: *** [__headers] Error 2
make: *** [vmlinux] Error 2

Rename the symbol in unifdef.c to parseline to avoid this conflicting
declaration.

Otherwise Jakub says we could add a -D_POSIX_C_SOURCE=200112L as a
workaround to unifdef CFLAGS, but this seems like it would be less
desirable in the long term.

Signed-off-by: Kyle McMartin <kyle@redhat.com>