Add missing library to standalone libpq build on Win32.

Hiroshi Saito

Author: mhagander

src/interfaces/libpq/win32.mak

@@ -197,7 +197,7 @@ CPP_SBRS=.
 RSC_PROJ=/l 0x409 /fo"$(INTDIR)\libpq.res"
 
 LINK32=link.exe
-LINK32_FLAGS=kernel32.lib user32.lib advapi32.lib shfolder.lib wsock32.lib secur32.lib $(SSL_LIBS)  $(KFW_LIB) $(ADD_SECLIB) \
+LINK32_FLAGS=kernel32.lib user32.lib advapi32.lib shfolder.lib wsock32.lib ws2_32.lib secur32.lib $(SSL_LIBS)  $(KFW_LIB) $(ADD_SECLIB) \
  /nologo /subsystem:windows /dll $(LOPT) /incremental:no \
  /pdb:"$(OUTDIR)\libpqdll.pdb" /machine:$(CPU) \
  /out:"$(OUTDIR)\$(OUTFILENAME).dll"\