Don't assume that egrep and fgrep exist, as POSIX 1003.1-2001 no

Don't assume that egrep and fgrep exist, as POSIX 1003.1-2001 no
longer requires them.

* Makefile.am (maintainer-check): Use grep -E and grep -F instead
of egrep and fgrep.  Omit unnecessary -E and -F.
Fix quoting typo -- "fgrep '\$${'" should have been "fgrep '$${'".
* lib/am/distdir.am (distdir): fgrep -> grep -F.
Use $(), not ${}, for Make variables.
* lib/am/texinfos.am (install-info-am, uninstall-info-am):
fgrep -> grep
* m4/make.m4 (AM_MAKE_INCLUDE): Likewise.
* tests/defs: Set FGREP and EGREP.

* tests/aclocali.test, tests/acoutput2.test, tests/all.test,
tests/ansi.test, tests/ansi4.test, tests/colon3.test,
tests/cond21.test, tests/condlib.test, tests/confh4.test,
tests/confsub.test, tests/cxxansi.test, tests/cxxo.test,
tests/depend4.test, tests/discover.test, tests/distname.test,
tests/dup3.test, tests/empty4.test, tests/fo.test,
tests/implicit.test, tests/insh2.test, tests/interp.test,
tests/lex.test, tests/lex3.test, tests/lex4.test,
tests/libobj5.test, tests/libobj7.test, tests/make.test,
tests/makevars.test, tests/nostdinc.test, tests/parse.test,
tests/pluseq.test, tests/pluseq4.test, tests/pluseq6.test,
tests/pr2.test, tests/pr9.test, tests/seenc.test,
tests/specflags.test, tests/specflags3.test,
tests/specflags6.test, tests/subobj.test, tests/subobj2.test,
tests/suffix3.test, tests/texinfo.test, tests/texinfo6.test,
tests/texinfo8.test, tests/vtexi.test, tests/yacc3.test,
tests/yacc6.test: fgrep -> $FGREP, egrep -> $EGREP