Record full paths of programs sought by "configure".

Previously we had a mix of uses of AC_CHECK_PROG[S] and AC_PATH_PROG[S].
The only difference between those macros is that the latter emits the
full path to the program it finds, eg "/usr/bin/prove", whereas the
former emits just "prove".  Let's standardize on always emitting the
full path; this is better for documentation of the build, and it might
prevent some types of failures if later build steps are done with
a different PATH setting.

I did not touch the AC_CHECK_PROG[S] calls in ax_pthread.m4 and
ax_prog_perl_modules.m4.  There seems no need to make those diverge from
upstream, since we do not record the programs sought by the former, while
the latter's call to AC_CHECK_PROG(PERL,...) will never be reached.

Discussion: https://postgr.es/m/25937.1501433410@sss.pgh.pa.us

Author: tglsfdc

config/docbook.m4

@@ -3,7 +3,7 @@
 # PGAC_PROG_NSGMLS
 # ----------------
 AC_DEFUN([PGAC_PROG_NSGMLS],
-[AC_CHECK_PROGS([NSGMLS], [onsgmls nsgmls])])
+[AC_PATH_PROGS([NSGMLS], [onsgmls nsgmls])])
 
 
 # PGAC_CHECK_DOCBOOK(VERSION)

config/programs.m4

@@ -229,7 +229,7 @@ AC_DEFUN([PGAC_CHECK_GETTEXT],
                  [AC_MSG_ERROR([a gettext implementation is required for NLS])])
   AC_CHECK_HEADER([libintl.h], [],
                   [AC_MSG_ERROR([header file <libintl.h> is required for NLS])])
-  AC_CHECK_PROGS(MSGFMT, msgfmt)
+  AC_PATH_PROGS(MSGFMT, msgfmt)
   if test -z "$MSGFMT"; then
     AC_MSG_ERROR([msgfmt is required for NLS])
   fi
@@ -238,8 +238,8 @@ AC_DEFUN([PGAC_CHECK_GETTEXT],
     pgac_cv_msgfmt_flags=-c
 fi])
   AC_SUBST(MSGFMT_FLAGS, $pgac_cv_msgfmt_flags)
-  AC_CHECK_PROGS(MSGMERGE, msgmerge)
-  AC_CHECK_PROGS(XGETTEXT, xgettext)
+  AC_PATH_PROGS(MSGMERGE, msgmerge)
+  AC_PATH_PROGS(XGETTEXT, xgettext)
 ])# PGAC_CHECK_GETTEXT