scratch_buffer: Avoid conflict with prepr. macros owned by the system. * lib/scratch_buffer.h: Don't include <libc-config.h>. Define _GL_LIKELY, _GL_UNLIKELY. Include malloc/scratch_buffer.gl.h instead of malloc/scratch_buffer.h. * modules/scratch_buffer (Depends-on): Add builtin-expect. (Makefile.am): Arrange to create malloc/scratch_buffer.gl.h from malloc/scratch_buffer.h.