Better DLL support on x86-64.
Better DLL support on x86-64.

- Add a macro TCC_OUTPUT_DLL_WITH_PLT.
-- Now, the DLL with PLT support works only on x86-64, but we may be able to support it on all architectures eventually.
- Define TCC_OUTPUT_DLL_WITH_PLT when target architecture is x86-64.
- Current status (x86-64):
-- Main program should be able to call functions in shared objects.
-- Main program should be able to use global variables in shared objects.
-- Shared objects should be able to call functions in main  program.
-- Shared objects can NOT use global variables in main program.
- To fix the last issue, we may need to add support of -fPIC option in our code generator.

avih/tinycc,FriedBreakfast/tcc,andreiw/tinycc,run4flat/tinycc,mobiphil/tinnycc,mobiphil/tinnycc,Saectar/inherpreter,alfonsokim/tinycc,soywiz/tinycc,andrewchambers/tccmirror,FriedBreakfast/tcc,acook/tinycc,mirror/tinycc,gfwilliams/tinycc,code4game/tinycc,ftdi-paul-jiao/tinyCC,andrewchambers/tccmirror,fstudio/tinycc,Wallbraker/DCPU-TCC,mobiphil/tinnycc,andreiw/tinycc,yousong/tinycc,Saectar/inherpreter,leeduhem/tinycc,leeduhem/tinycc,mingodad/tinycc,xcm/tcc,rchandramouli/tinycc,Archs/TinyCC,gfwilliams/tinycc,metaeducation/tcc,shinh/nacltcc,FriedBreakfast/tcc,seyko2/tinycc,seyko2/tinycc,Archs/TinyCC,metaeducation/tcc,metaeducation/tcc,xcm/tcc,fstudio/tinycc,acook/tinycc,run4flat/tinycc,Wallbraker/DCPU-TCC,gfwilliams/tinycc,seyko2/tinycc,gfwilliams/tinycc,yousong/tinycc,melkior/tinycc,ftdi-paul-jiao/tinyCC,avih/tinycc,andrewchambers/tccmirror,Saectar/inherpreter,acook/tinycc,xcm/tcc,soywiz/tinycc,alfonsokim/tinycc,mitake/tinycc,alfonsokim/tinycc,Archs/TinyCC,alfonsokim/tinycc,Archs/TinyCC,Wallbraker/DCPU-TCC,fstudio/tinycc,andrewchambers/tccmirror,andrewchambers/tccmirror,mingodad/tinycc,mitake/tinycc,FriedBreakfast/tcc,soywiz/tinycc,melkior/tinycc,shinh/nacltcc,gfwilliams/tinycc,rchandramouli/tinycc,ftdi-paul-jiao/tinyCC,andreiw/tinycc,shinh/nacltcc,soywiz/tinycc,yousong/tinycc,mirror/tinycc,leeduhem/tinycc,avih/tinycc,fstudio/tinycc,mirror/tinycc,metaeducation/tcc,seyko2/tinycc,shinh/nacltcc,run4flat/tinycc,yousong/tinycc,shinh/nacltcc,melkior/tinycc,mingodad/tinycc,FriedBreakfast/tcc,fstudio/tinycc,seyko2/tinycc,mitake/tinycc,rchandramouli/tinycc,acook/tinycc,rchandramouli/tinycc,run4flat/tinycc,code4game/tinycc,metaeducation/tcc,melkior/tinycc,mirror/tinycc,melkior/tinycc,code4game/tinycc,Archs/TinyCC,run4flat/tinycc,Saectar/inherpreter,leeduhem/tinycc,mitake/tinycc,Saectar/inherpreter,mobiphil/tinnycc,mingodad/tinycc,alfonsokim/tinycc,leeduhem/tinycc,rchandramouli/tinycc,ftdi-paul-jiao/tinyCC,avih/tinycc