build: Need sdl needs 'check false'

If no 'check' is provided, we assume that the checks passed.
If pkg-config is specified, but no other check, use 'check false'
to ensure the module is disable if the pkg-config checks don't pass.

Also travis now does 'make all' so that any module extensions are
also built, and add a dependency on libhiredis-dev to test
building the redis extension.

Signed-off-by: Steve Bennett <steveb@workware.net.au>

.travis.yml

@@ -4,8 +4,9 @@ addons:
   apt:
     packages:
       - libsqlite3-dev
+      - libhiredis-dev
 before_script:
   - ./configure --maintainer --full --allextmod --disable-docs
 script:
-  - make test
+  - make all test
   - ./test-bootstrap-jim

auto.def

@@ -163,7 +163,7 @@ dict set extdb info {
     readline { pkg-config readline check {[cc-check-function-in-lib readline readline]} libdep lib_readline}
     rlprompt { dep readline }
     tree     { dep oo }
-    sdl      { pkg-config {SDL2_gfx, SDL2_ttf* | SDL_gfx} }
+    sdl      { pkg-config {SDL2_gfx, SDL2_ttf* | SDL_gfx} check false }
     signal   { check {[have-feature sigaction]} }
     sqlite3  { pkg-config sqlite3 check {[cc-check-function-in-lib sqlite3_prepare_v2 sqlite3]} libdep lib_sqlite3_prepare_v2 }
     redis    { pkg-config hiredis check {[cc-check-function-in-lib redisConnect hiredis]} libdep lib_redisConnect }