configure.ac: Redefine AC_PROG_CC to cause errors
configure.ac: Redefine AC_PROG_CC to cause errors

ZNC is written in C++ and doesn't need a C compiler. This redefine let's us
catch code which accidentally uses the C compiler.

Currently this means that we break due to gl_VISIBILITY.

Signed-off-by: Uli Schlachter <346c0ad49ac8427b61b3b55abbe37dc0ebd524f2@znc.in>

evilnet/znc,psychon/znc,Adam-/znc,Mikaela/znc,jreese/znc,aarondunlap/znc,ollie27/znc,Adam-/znc,wolfy1339/znc,badloop/znc,Kriechi/znc,jreese/znc,wolfy1339/znc,withinsoft/znc,Mikaela/znc,aarondunlap/znc,anthonyryan1/znc,Mikaela/znc,kashike/znc,jpnurmi/znc,Hasimir/znc,anthonyryan1/znc,jantman/znc,KielBNC/znc,KiNgMaR/znc,dgw/znc,jreese/znc,jpnurmi/znc,Adam-/znc,BtbN/znc,Zarthus/znc,reedloden/znc,withinsoft/znc,anthonyryan1/znc,markusj/znc,wolfy1339/znc,Mkaysi/znc,evilnet/znc,Kriechi/znc,TuffLuck/znc,ollie27/znc,aarondunlap/znc,badloop/znc,DarthGandalf/znc,badloop/znc,TuffLuck/znc,Phansa/znc,anthonyryan1/znc,badloop/znc,Mkaysi/znc,markusj/znc,trisk/znc,ollie27/znc,reedloden/znc,withinsoft/znc,jreese/znc,Mkaysi/znc,jpnurmi/znc,BtbN/znc,Kriechi/znc,KiNgMaR/znc,anthonyryan1/znc,reedloden/znc,dgw/znc,BtbN/znc,Hasimir/znc,Adam-/znc,trisk/znc,jpnurmi/znc,aarondunlap/znc,Mkaysi/znc,KielBNC/znc,jpnurmi/znc,evilnet/znc,withinsoft/znc,Hasimir/znc,TingPing/znc,evilnet/znc,jantman/znc,psychon/znc,aarondunlap/znc,Phansa/znc,jpnurmi/znc,DarthGandalf/znc,jantman/znc,jreese/znc,elyscape/znc,trisk/znc,Adam-/znc,withinsoft/znc,Kriechi/nobnc,Zarthus/znc,Hasimir/znc,TuffLuck/znc,znc/znc,Adam-/znc,YourBNC/znc,ollie27/znc,ollie27/znc,Phansa/znc,DarthGandalf/znc,KiNgMaR/znc,TuffLuck/znc,TingPing/znc,DarthGandalf/znc,elyscape/znc,GLolol/znc,KiNgMaR/znc,Phansa/znc,Phansa/znc,aarondunlap/znc,Kriechi/znc,wolfy1339/znc,elyscape/znc,BtbN/znc,elyscape/znc,elyscape/znc,reedloden/znc,KielBNC/znc,kashike/znc,jreese/znc,Mkaysi/znc,markusj/znc,wolfy1339/znc,Kriechi/znc,TingPing/znc,YourBNC/znc,znc/znc,KielBNC/znc,trisk/znc,KielBNC/znc,badloop/znc,Zarthus/znc,Zarthus/znc,YourBNC/znc,znc/znc,Hasimir/znc,YourBNC/znc,trisk/znc,YourBNC/znc,jantman/znc,GLolol/znc,kashike/znc,wolfy1339/znc,BtbN/znc,dgw/znc,Mkaysi/znc,reedloden/znc,Zarthus/znc,TingPing/znc,TingPing/znc,Mikaela/znc,badloop/znc,markusj/znc,Adam-/znc,ollie27/znc,reedloden/znc,psychon/znc,KiNgMaR/znc,DarthGandalf/znc,kashike/znc,dgw/znc,anthonyryan1/znc,Mikaela/znc,markusj/znc,TuffLuck/znc,markusj/znc,TuffLuck/znc,znc/znc,KiNgMaR/znc,TuffLuck/znc,Kriechi/nobnc,GLolol/znc,Mkaysi/znc,jpnurmi/znc,evilnet/znc,YourBNC/znc,DarthGandalf/znc,GLolol/znc,psychon/znc,aarondunlap/znc,GLolol/znc,evilnet/znc,dgw/znc,jantman/znc,psychon/znc,Mikaela/znc,Hasimir/znc,withinsoft/znc,Zarthus/znc,KielBNC/znc,Mikaela/znc,anthonyryan1/znc,Kriechi/nobnc,kashike/znc,Kriechi/znc,znc/znc,BtbN/znc,znc/znc,jantman/znc,psychon/znc,Phansa/znc,dgw/znc,GLolol/znc,trisk/znc,elyscape/znc,badloop/znc,TingPing/znc,Hasimir/znc,kashike/znc