configure: use pkg-config helpers

This makes existing pkg-config uses as well as the libsdl checks
use the new pkg-config helper functions, which should be more
robust against broken systems.
Signed-off-by: Mans Rullgard <mans@mansr.com>

configure

@@ -2849,22 +2849,19 @@ check_mathfunc truncf
 # these are off by default, so fail if requested and not available
 enabled avisynth   && require2 vfw32 "windows.h vfw.h" AVIFileInit -lavifil32
 enabled frei0r     && { check_header frei0r.h || die "ERROR: frei0r.h header not found"; }
-enabled libdirac   && add_cflags $(pkg-config --cflags dirac) &&
-                      require  libdirac libdirac_decoder/dirac_parser.h dirac_decoder_init $(pkg-config --libs dirac) &&
-                      require  libdirac libdirac_encoder/dirac_encoder.h dirac_encoder_init $(pkg-config --libs dirac)
+enabled libdirac   && require_pkg_config dirac                          \
+    "libdirac_decoder/dirac_parser.h libdirac_encoder/dirac_encoder.h"  \
+    "dirac_decoder_init dirac_encoder_init"
 enabled libfaac    && require2 libfaac "stdint.h faac.h" faacEncGetVersion -lfaac
 enabled libgsm     && require  libgsm gsm/gsm.h gsm_create -lgsm
 enabled libmp3lame && require  "libmp3lame >= 3.98.3" lame/lame.h lame_set_VBR_quality -lmp3lame
 enabled libnut     && require  libnut libnut.h nut_demuxer_init -lnut
 enabled libopencore_amrnb  && require libopencore_amrnb opencore-amrnb/interf_dec.h Decoder_Interface_init -lopencore-amrnb
 enabled libopencore_amrwb  && require libopencore_amrwb opencore-amrwb/dec_if.h D_IF_init -lopencore-amrwb
-enabled libopencv  && { check_lib opencv/cv.h cvCreateImageHeader $(pkg-config --libs opencv) ||
-                        die "ERROR: libopencv not found"; }
+enabled libopencv  && require_pkg_config opencv opencv/cv.h cvCreateImageHeader
 enabled libopenjpeg && require libopenjpeg openjpeg.h opj_version -lopenjpeg
-enabled librtmp    && { check_lib librtmp/rtmp.h RTMP_Socket $(pkg-config --libs librtmp) ||
-                        die "ERROR: librtmp not found or RTMP_Socket() missing, librtmp version must be >= 2.2.f"; }
-enabled libschroedinger && add_cflags $(pkg-config --cflags schroedinger-1.0) &&
-                           require libschroedinger schroedinger/schro.h schro_init $(pkg-config --libs schroedinger-1.0)
+enabled librtmp    && require_pkg_config librtmp librtmp/rtmp.h RTMP_Socket
+enabled libschroedinger && require_pkg_config schroedinger-1.0 schroedinger/schro.h schro_init
 enabled libspeex   && require  libspeex speex/speex.h speex_decoder_init -lspeex
 enabled libtheora  && require  libtheora theora/theoraenc.h th_info_init -ltheoraenc -ltheoradec -logg
 enabled libvorbis  && require  libvorbis vorbis/vorbisenc.h vorbis_info_init -lvorbisenc -lvorbis -logg
@@ -2889,11 +2886,7 @@ if enabled libdc1394; then
     die "ERROR: No version of libdc1394 found "
 fi
 
-SDL_CONFIG="${cross_prefix}sdl-config"
-if "${SDL_CONFIG}" --version > /dev/null 2>&1; then
-    sdl_cflags=$("${SDL_CONFIG}" --cflags)
-    sdl_libs=$("${SDL_CONFIG}" --libs)
-    check_func_headers SDL.h SDL_Init $sdl_cflags $sdl_libs &&
+if check_pkg_config sdl SDL.h SDL_Init; then
     check_cpp_condition SDL.h "(SDL_MAJOR_VERSION<<16 | SDL_MINOR_VERSION<<8 | SDL_PATCHLEVEL) >= 0x010201" $sdl_cflags &&
     enable sdl &&
     check_struct SDL.h SDL_VideoInfo current_w $sdl_cflags && enable sdl_video_size