remove install-sh, INSTALL and doc/texinfo.tex

These are generated files.  Generated file should not be included
in source control.

Here's a snippet of the output form autoreconf -vif...

configure.ac:7: installing './install-sh'
Makefile.am: installing './INSTALL'
doc/Makefile.am:1: installing 'doc/texinfo.tex'
Merge pull request #2 from reubenhwk/buildsys-cleaning

remove install-sh, INSTALL and doc/texinfo.tex