make build of PDF optional to avoid LaTeX dependency

Fixes #95.

INSTALL.md

@@ -71,9 +71,15 @@ The steps in building Stow are:
 
     to avoid a superfluous `use lib` line in your stow executable.
 
-3.  Type `perl Build.PL`.
+3.  If you have LaTeX and texinfo installed and want to build a PDF
+    version of the manual, type:
 
-4.  Type `./Build install` to install the various files.  As noted
+        make pdf
+
+4.  Type `perl Build.PL`.  If you skipped step 3 and see a warning
+    about `manual.pdf` being missing, you can safely ignore it.
+
+5.  Type `./Build install` to install the various files.  As noted
     above, this installs fewer files than the Autotools installation.
 
 Basic Installation via Autotools
@@ -105,6 +111,10 @@ The steps in building Stow are:
     line into the generated stow script to ensure that it can always
     locate the Perl modules without needing to manually set `PERL5LIB`.
 
+4.  If you have LaTeX and texinfo installed and want to build a PDF
+    version of the manual, type:
+
+        make pdf
 
 Installation Names
 ------------------

Makefile.am

@@ -22,7 +22,7 @@ PDF = doc/manual.pdf
 HTML = doc/manual-single.html
 dist_doc_DATA = \
 	README.md INSTALL.md \
-	$(PDF) $(HTML) doc/version.texi \
+	$(HTML) doc/version.texi \
 	ChangeLog doc/ChangeLog.OLD
 
 # automake magic to define where *_DATA files get installed:
@@ -97,7 +97,7 @@ $(TESTS_OUT):
 CPAN_FILES = MANIFEST MANIFEST.SKIP Build.PL META.yml META.json
 EXTRA_DIST = \
 	bin/stow.in bin/chkstow.in lib/Stow.pm.in lib/Stow/Util.pm.in \
-	doc/manual-split \
+	$(PDF) doc/manual-split \
 	$(TESTS) t/testutil.pm \
 	$(DEFAULT_IGNORE_LIST) \
 	$(CPAN_FILES)
@@ -237,6 +237,8 @@ $(HTML): $(doc_deps)
 		-c USE_TITLEPAGE_FOR_TITLE=1 --no-split -o $@ \
 		`test -f 'doc/stow.texi' || echo '$(srcdir)/'`doc/stow.texi
 
+pdf: $(PDF)
+
 $(PDF): $(doc_deps)
 	TEXINPUTS="$(am__TEXINFO_TEX_DIR)$(PATH_SEPARATOR)$$TEXINPUTS" \
 	MAKEINFO='$(MAKEINFO) $(AM_MAKEINFOFLAGS) $(MAKEINFOFLAGS) -I doc -I $(srcdir)/doc' \

doc/HOWTO-RELEASE

@@ -38,6 +38,7 @@ Release procedure
         eval `perl -V:siteprefix`
         automake --add-missing
         ./configure --prefix=$siteprefix && make
+        make pdf
 
       (N.B. the CPAN distribution will contain these files, whereas
       the GNU distribution will not.)