configure.ac: add some helper macros
configure.ac: add some helper macros

library check related variable maintenance -> *_INCLUDES / *_LIBS

CLEAR_LIBVARS / LIBCHECK_PROLOGUE / LIBCHECK_EPILOGUE

Change-Id: I72e292dc1f69b02f69a26639308f247db0471e2b
(cherry picked from commit 4ef144779260bdd4f4b06d2ccf67f6756e1f0f57)

matanbs/webm.libwebp,abwiz0086/webm.libwebp,iniwf/webm.libwebp,ericmckean/webm.libwebp,kalli123/webm.libwebp,ericmckean/webm.libwebp,zofuthan/libwebp,comoyo/gonzo-libwebp,kalli123/webm.libwebp,matanbs/webm.libwebp,comoyo/gonzo-libwebp,ya7lelkom/libwebp,gshORTON/webm.libwebp,zofuthan/libwebp,Maria1099/webm.libwebp,reimaginemedia/webm.libwebp,appunite/libwebp,Maria1099/webm.libwebp,ya7lelkom/libwebp,yohunl/libwebp,comoyo/gonzo-libwebp,PKRoma/libwebp,zofuthan/libwebp,gshORTON/webm.libwebp,altogother/webm.libwebp,appunite/libwebp,reimaginemedia/webm.libwebp,Aexyn/libwebp,Suvarna1488/webm.libwebp,jiehu5114/libwebp,ttyangf/libwebp,yohunl/libwebp,appunite/libwebp,ya7lelkom/libwebp,cysp/libwebp,keane83/BLE_IM,jacklicn/libwebp,rxl194/libwebp,appunite/libwebp,jacklicn/libwebp,cysp/libwebp,jacklicn/libwebp,ttyangf/libwebp,abwiz0086/webm.libwebp,Aexyn/libwebp,altogother/webm.libwebp,rxl194/libwebp,kleopatra999/webm.libwebp,ericmckean/webm.libwebp,iniwf/webm.libwebp,imazen/libwebp,ericmckean/webm.libwebp,reimaginemedia/webm.libwebp,Acidburn0zzz/webm.libwebp,Acidburn0zzz/webm.libwebp,altogother/webm.libwebp,PKRoma/libwebp,webmproject/libwebp,keane83/BLE_IM,jiehu5114/libwebp,Maria1099/webm.libwebp,Aexyn/libwebp,altogother/webm.libwebp,imazen/libwebp,iniwf/webm.libwebp,ya7lelkom/libwebp,kalli123/webm.libwebp,jacklicn/libwebp,keane83/BLE_IM,webmproject/libwebp,kim42083/webm.libwebp,redengineer/libwebp,kim42083/webm.libwebp,Suvarna1488/webm.libwebp,webmproject/libwebp,matanbs/webm.libwebp,kim42083/webm.libwebp,appunite/libwebp,Suvarna1488/webm.libwebp,reimaginemedia/webm.libwebp,Tekserve/libwebp,ttyangf/libwebp,jiehu5114/libwebp,webmproject/libwebp,cysp/libwebp,Maria1099/webm.libwebp,kleopatra999/webm.libwebp,kim42083/webm.libwebp,imazen/libwebp,gshORTON/webm.libwebp,webmproject/libwebp,matanbs/webm.libwebp,Tekserve/libwebp,zofuthan/libwebp,ya7lelkom/libwebp,redengineer/libwebp,jacklicn/libwebp,iniwf/webm.libwebp,rxl194/libwebp,altogother/webm.libwebp,PKRoma/libwebp,kim42083/webm.libwebp,imazen/libwebp,comoyo/gonzo-libwebp,Aexyn/libwebp,abwiz0086/webm.libwebp,jiehu5114/libwebp,appunite/libwebp,matanbs/webm.libwebp,Acidburn0zzz/webm.libwebp,ttyangf/libwebp,zofuthan/libwebp,PKRoma/libwebp,Tekserve/libwebp,ericmckean/webm.libwebp,redengineer/libwebp,abwiz0086/webm.libwebp,redengineer/libwebp,iniwf/webm.libwebp,yohunl/libwebp,cysp/libwebp,gshORTON/webm.libwebp,Acidburn0zzz/webm.libwebp,yohunl/libwebp,comoyo/gonzo-libwebp,Acidburn0zzz/webm.libwebp,kalli123/webm.libwebp,jiehu5114/libwebp,keane83/BLE_IM,kleopatra999/webm.libwebp,ttyangf/libwebp,PKRoma/libwebp,imazen/libwebp,Suvarna1488/webm.libwebp,rxl194/libwebp,PKRoma/libwebp,reimaginemedia/webm.libwebp,abwiz0086/webm.libwebp,gshORTON/webm.libwebp,Maria1099/webm.libwebp,rxl194/libwebp,kalli123/webm.libwebp,comoyo/gonzo-libwebp,Tekserve/libwebp,redengineer/libwebp,Aexyn/libwebp,Suvarna1488/webm.libwebp,kleopatra999/webm.libwebp,keane83/BLE_IM,kleopatra999/webm.libwebp,comoyo/gonzo-libwebp,yohunl/libwebp