unifdef installation instructions


To build, type `make`. You can adjust the compilation options
using the POSIX standard CFLAGS and LDFLAGS make variables.

To install in your home directory, type `make install`
or to install in /usr type `make prefix=/usr install`.
See the start of the Makefile for the install location
variables.


Non-portable dependencies:

This program requires the BSD err.h functions, and C99 stdbool.h.


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