Fix Windows build error: unresolved if_nametoindex symbol

[FeBe95]

Adds iphlpapi.lib to the Windows library list in config.w32.

Recent versions of the bundled libcurl_a.lib reference if_nametoindex (used for IPv6 scoped address handling), which on Windows lives in iphlpapi.dll. Without linking against iphlpapi.lib, the build fails with:

libcurl_a.lib(url.obj) : error LNK2019: unresolved external symbol "__imp_if_nametoindex" referenced in function "zonefrom_url".
C:\php-sdk\phpmaster\vs17\x64\php-src\x64\Release_TS\php_pdo_snowflake.dll : fatal error LNK1120: 1 unresolved externals
NMAKE : fatal error U1077: ""link.exe" @"C:\php-sdk\phpmaster\vs17\x64\php-src\x64\Release_TS\resp\PDO_SNOWFLAKE_GLOBAL_OBJS.txt" 

iphlpapi.lib is a standard Windows SDK library and is always available in VS16/VS17 build environments.

Command that triggered this error:

.\scripts\run_build_pdo_snowflake.bat x64 Release VS17 8.4.17 C:\php-sdk

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[FeBe95]

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