DOC: fix a few typos in the documentation

This commit deals with a few misspells in the documentation.
diff --git a/doc/lua.txt b/doc/lua.txt
index d513a67..dcb9b8f 100644
--- a/doc/lua.txt
+++ b/doc/lua.txt
@@ -35,7 +35,7 @@
 modify the HAProxy source code, but to write their own control code. Lua is
 encountered very often in the software industry, and in some open source
 projects. It is easy to understand, efficient, light without external
-dependancies, and leaves the resource control to the implementation. Its design
+dependencies, and leaves the resource control to the implementation. Its design
 is close to the HAProxy philosophy which uses components for what they do
 perfectly.
 
@@ -473,7 +473,7 @@
 before the last Lua execution.
 
 Lua can immediately stop its execution if an error occurs. This system uses also
-the longjmp system. In HAProxy, we try to use this sytem only for unrecoverable
+the longjmp system. In HAProxy, we try to use this system only for unrecoverable
 errors. Maybe some trivial errors target an exception, but we try to remove it.
 
 It seems that Lua uses the longjmp system for having a behaviour like the java
@@ -917,7 +917,7 @@
 HTTP actions
 ============
 
-   ... comming soon ...
+   ... coming soon ...
 
 Lua is fast, but my service require more execution speed
 ========================================================