Windows: fix "Include" of UNC paths #1130

Job	Run time
Empty APLOGNO() test	26s
Default	4m 47s
All-static modules	4m 48s
Prefork MPM, all-modules (except cgid)	5m 14s
Worker MPM, all-modules	5m 33s
Shared MPMs, all-modules	5m 30s
Event MPM, all-modules, mod_cgid only	6m 0s
Event MPM, all-modules, no CMSG_DATA	5m 7s
Default, all-modules + install	5m 58s
Default, all-modules, random test order	5m 37s
GCC 10 maintainer-mode w/-Werror, install + VPATH	3m 19s
All-modules, APR 1.7.4, APR-util 1.6.3	6m 13s
APR 1.8.x, APR-util 1.7.x	6m 17s
Pool-debug	6m 6s
Shared MPMs (event), pool-debug, SSL/TLS variants	10m 7s
Shared MPMs (worker), pool-debug, SSL/TLS variants	10m 22s
Shared MPMs (prefork), pool-debug, SSL/TLS variants	9m 51s
litmus WebDAV tests	3m 33s
litmus WebDAV tests, APR trunk, LMDB	3m 59s
Regenerate ap_expr	5m 31s
APR 1.7.4, APR-util 1.6.3, LDAP	5m 46s
APR 1.7.x, APR-util 1.7.x, LDAP	6m 6s
APR trunk thread debugging	5m 50s
UBSan	6m 3s
ASan	6m 37s
ASan, pool-debug	7m 21s
HTTP/2 test suite	5m 52s
MOD_TLS test suite	4m 49s
Configured w/reduced exports	2m 9s
OpenSSL 3.1	7m 33s
OpenSSL 3.2 -Werror	8m 36s
OpenSSL 3.2 no-engine	7m 33s
OpenSSL 3.3 no-engine -Werror	8m 47s
	3h 17m 20s

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