Fix serving of raw wiki files other than .md (#5814)

* Fix serving of raw wiki files other than .md

Closes #4690.
Closes #4395.

Signed-off-by: Gabriel Silva Simões <simoes.sgabriel@gmail.com>

* Simplify code at routers/repo/wiki.go

Signed-off-by: Gabriel Silva Simões <simoes.sgabriel@gmail.com>

* Add more files to user2/repo1.wiki for testing

Signed-off-by: Gabriel Silva Simões <simoes.sgabriel@gmail.com>

* Update macaron to v1.3.2

Signed-off-by: Gabriel Silva Simões <simoes.sgabriel@gmail.com>

* Add tests for WikiRaw

Signed-off-by: Gabriel Silva Simões <simoes.sgabriel@gmail.com>

* Fix NewResponseWriter usage due to macaron update

Signed-off-by: Gabriel Silva Simões <simoes.sgabriel@gmail.com>

* Add raw to reserved wiki names

Signed-off-by: Gabriel Silva Simões <simoes.sgabriel@gmail.com>

Author: gabrielsimoes

Gopkg.lock

@@ -0,0 +1,2 @@
+x
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integrations/gitea-repositories-meta/user2/repo1.wiki.git/objects/0c/f15c3f66ec8384480ed9c3cf87c9e97fbb0ec3

@@ -0,0 +1 @@
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integrations/gitea-repositories-meta/user2/repo1.wiki.git/objects/32/5dc4f8e9344e6668f21536a69d5f1d4ed53ca3

@@ -0,0 +1,2 @@
+x
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integrations/gitea-repositories-meta/user2/repo1.wiki.git/objects/71/911bf48766c7181518c1070911019fbb00b1fc

@@ -1 +1 @@
-2c54faec6c45d31c1abfaecdab471eac6633738a
+0cf15c3f66ec8384480ed9c3cf87c9e97fbb0ec3

integrations/gitea-repositories-meta/user2/repo1.wiki.git/objects/72/fc6251cc648e914c10009d31431fa2e38b9a20

@@ -22,7 +22,7 @@ import (
 )
 
 var (
-	reservedWikiNames = []string{"_pages", "_new", "_edit"}
+	reservedWikiNames = []string{"_pages", "_new", "_edit", "raw"}
 	wikiWorkingPool   = sync.NewExclusivePool()
 )