m4: Fix ./configure --disable-ocaml

OCaml is required to compile libguestfs, however we should still be
able to disable the OCaml bindings.  This didn't work because using
--disable-ocaml caused various configure tests to be skipped which are
required to compile the daemon.  In particular the check for
caml_alloc_initialized_string, resulting in this error:

pcre-c.c:47:1: error: static declaration of ‘caml_alloc_initialized_string’ follows non-static declaration
 caml_alloc_initialized_string (mlsize_t len, const char *p)
 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Also OCaml gettext is not required by libguestfs.  There are no *.ml
files used by libguestfs which require translation.

Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=2108425
Fixes: https://bugs.gentoo.org/820053
Fixes: commit 733d2182b6

Makefile.am

@@ -37,7 +37,6 @@ SUBDIRS += include lib docs examples
 SUBDIRS += common/mlutils
 SUBDIRS += bundled/ocaml-augeas
 SUBDIRS += common/mlpcre
-SUBDIRS += common/mlgettext
 if ENABLE_DAEMON
 SUBDIRS += daemon
 endif
@@ -208,9 +207,8 @@ maintainer-upload-website:
 #  docs/C_SOURCE_FILES
 #                 - source files scanned for internal documentation
 #  po/POTFILES    - files with ordinary extensions, but not OCaml files
-#  po/POTFILES-ml - OCaml files, which need a special tool to translate
 
-dist-hook: docs/C_SOURCE_FILES po/POTFILES po/POTFILES-ml
+dist-hook: docs/C_SOURCE_FILES po/POTFILES
 
 # This has to be in the top-level Makefile.am so that we have access
 # to DIST_SUBDIRS.
@@ -446,6 +444,7 @@ maintainer-check-extra-dist:
 	  cd common; git ls-files | sed 's,^,common/,' ) | \
 	  grep -v '^common$$' | \
 	  grep -v '^common/mlcustomize/' | \
+	  grep -v '^common/mlgettext/' | \
 	  grep -v '^common/mlprogress/' | \
 	  grep -v '^common/mltools/' | \
 	  grep -v '^common/mlv2v/' | \