general/5821: Hostnames with underscore produce "Client sent malformed Host header"

[Detlev Beutner <db...@acg-gmbh.de>]

>Number:         5821
>Category:       general
>Synopsis:       Hostnames with underscore produce "Client sent malformed Host header"
>Confidential:   no
>Severity:       critical
>Priority:       medium
>Responsible:    apache
>State:          open
>Class:          sw-bug
>Submitter-Id:   apache
>Arrival-Date:   Tue Feb 29 04:20:00 PST 2000
>Closed-Date:
>Last-Modified:
>Originator:     dbeutner@acg-gmbh.de
>Release:        1.3.12 (since 1.3.11)
>Organization:
apache
>Environment:
WinNT 4.0, but occurs on all platforms
>Description:
See above (title). See also PR's ## 5720, 5722, 5736 (reported against 1.3.11,
but still it occurs in 1.3.12).
>How-To-Repeat:
With a hostname with an underscore (like my localhost: "sapsw14_2").
>Fix:
An underscore is a valid char in a hostname, but it is not recognized as this.
See also PR # 5720 for details.
>Release-Note:
>Audit-Trail:
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