build: move the syntax files out of the doc/ directory

They are not documentation, they are functional elements of nano.

Makefile.am

@@ -2,6 +2,10 @@ AUTOMAKE_OPTIONS = gnu no-dependencies
 
 SUBDIRS = doc m4 po src
 
+if USE_COLOR
+SUBDIRS += syntax
+endif
+
 EXTRA_DIST = ChangeLog.pre-2.1 IMPROVEMENTS README.GIT nano.spec
 
 ACLOCAL_AMFLAGS = -I m4

configure.ac

@@ -752,10 +752,10 @@ AC_CONFIG_FILES([
 Makefile
 doc/Makefile
 doc/nanorc.sample
-doc/syntax/Makefile
 m4/Makefile
 po/Makefile.in
 src/Makefile
+syntax/Makefile
 nano.spec
 ])
 

doc/Makefile.am

 SUBDIRS =
 BUILT_SOURCES =
 
-if USE_COLOR
-SUBDIRS += syntax
-endif
-
 dist_html_DATA = faq.html
 
 dist_man_MANS = nano.1 rnano.1