Changes in version 1.13:

File diagnostics have been reformatted as 'PROGRAM: FILE: MESSAGE'.

Diagnostics caused by invalid arguments to command-line options now show the
argument and the name of the option.

The variable MAKEINFO has been added to configure and Makefile.in.

It has been documented in INSTALL that when choosing a C standard, the POSIX
features need to be enabled explicitly:
  ./configure CFLAGS+='--std=c99 -D_XOPEN_SOURCE=500'
