Clean up Lua probes for headers and libs

Use the version reported by LUABIN to look for headers and libs.
Previously you could get mismatched binary and headers (e.g.
if you install packages lua5.3 and liblua5.2-dev on Debian you
would get LUABIN from 5.3 but headers and libraries from 5.2
- now configure will fail to find the matching headers and not
try to run Lua tests), and do a versioned search in /usr/local/include
which fixes the CI failure for Lua on macOS (presumably homebrew
recently started to version this path).

CHANGES.current

@@ -7,6 +7,9 @@ the issue number to the end of the URL: https://github.com/swig/swig/issues/
 Version 4.0.0 (in progress)
 ===========================
 
+2018-06-06: olly
+	    [Lua] Improve configure probes for Lua headers and libs used in testsuite.
+
 2018-05-15: kwwette
             [Octave] add support for version 4.4
             - Should not introduce any user-visible incompatibilities

configure.ac

@@ -2399,35 +2399,36 @@ else
 if test "x$LUABIN" = xyes; then
    # We look for a versioned Lua binary first, as there can be
    # multiple versions of Lua installed on some systems (like Debian).
-   # The search order should match the include-file and library search
-   # orders below (a Lua shared library built for one version may not
-   # work with a Lua binary of a different version).
    AC_PATH_PROGS(LUABIN, [lua5.4 lua5.3 lua5.2 lua5.1 lua])
 fi
 
 # check version: we need Lua 5.x
 if test "$LUABIN"; then
   AC_MSG_CHECKING(Lua version)
-  # if version 5.x
-  LUAV5=`$LUABIN -e 'if string.sub(_VERSION,5,5)=="5" then print "1" end'`
-  # if not version 5.0
-  LUAV51=`$LUABIN -e 'if string.sub(_VERSION,5,7)~="5.0" then print "1" end'`
-
-  if test -z "$LUAV5"; then
-    AC_MSG_WARN(Not Lua 5.x, SWIG does not support this version of Lua)
-    LUABIN=""
-  elif test -z "$LUAV51"; then
-    AC_MSG_RESULT(Lua 5.0.x)
+  [LUA_VERSION=`$LUABIN -e 'print(string.match(_VERSION, "%d+[.]%d+"))'`]
+  # For 5.0 and 5.1 header and libraries may be named using 50 or 51.
+  LUA_VERSION_NO_DOTS=
+  if test -n "$LUA_VERSION" ; then
+    AC_MSG_RESULT([Lua $LUA_VERSION.x])
   else
-    AC_MSG_RESULT(Lua 5.1 or later)
+    AC_MSG_RESULT([failed])
   fi
+  case $LUA_VERSION in
+    5.0) LUA_VERSION_NO_DOTS=50 ;;
+    5.1) LUA_VERSION_NO_DOTS=51 ;;
+    5.*) ;;
+    *)
+      AC_MSG_WARN([Not Lua 5.x, SWIG does not support this version of Lua])
+      LUABIN=""
+      ;;
+  esac
 fi
 
 if test "$LUABIN"; then
   AC_MSG_CHECKING(whether Lua dynamic loading is enabled)
   # using Lua to check Lua
   # lua 5.0 & 5.1 have different fn names
-  if test -z "$LUAV51"; then
+  if test "$LUA_VERSION" = "5.0"; then
     LUADYNAMICLOADLIB=`$LUABIN -e '_,_,c=loadlib("no_such_lib","") if c~="absent" then print "1" end'`
   else
     LUADYNAMICLOADLIB=`$LUABIN -e '_,_,c=package.loadlib("no_such_lib","") if c~="absent" then print "1" end'`
@@ -2456,7 +2457,12 @@ if test "$LUABIN"; then
       # The ordering of the include directories to search should match
       # the ordering of libraries to search in the library test below.
       inc=/usr/include
-      dirs="$inc/lua5.4 $inc/lua5.3 $inc/lua5.2 $inc/lua5.1 $inc/lua51 $inc/lua5.0 $inc/lua50 /usr/local/include"
+      incloc=/usr/local/include
+      dirs="$inc/lua$LUA_VERSION"
+      test -z "$LUA_VERSION_NO_DOTS" || dirs="$dirs $inc/lua$LUA_VERSION_NO_DOTS"
+      dirs="$dirs $incloc/lua$LUA_VERSION"
+      test -z "$LUA_VERSION_NO_DOTS" || dirs="$dirs $incloc/lua$LUA_VERSION_NO_DOTS"
+      dirs="$dirs $incloc"
       for i in $dirs; do
         #echo "$i"
         if test -r $i/lua.h; then
@@ -2479,11 +2485,13 @@ if test "$LUABIN"; then
   if test -n "$LUALIB"; then
     AC_CHECK_FILE($LUALIB/liblua.a,[LUALINK="-L$LUALIB -llua"],[LUABIN=])
   else
-    AC_SEARCH_LIBS(lua_close, [lua lua5.4 lua5.3 lua5.2 lua5.1 lua51 lua5.0 lua50], [LUALINK="-l$ac_lib"],[LUABIN=])
+    libs="lua lua$LUA_VERSION"
+    test -z "$LUA_VERSION_NO_DOTS" || libs="$libs lua$LUA_VERSION_NO_DOTS"
+    AC_SEARCH_LIBS(lua_close, [$libs], [LUALINK="-l$ac_lib"],[LUABIN=])
   fi
 
   # adding lualib for lua 5.0
-  if test -z "$LUAV51"; then # extra for lua 5.0
+  if test "$LUA_VERSION" = "5.0"; then
     LUALINK="$LUALINK -llualib"
   fi