supports for doc language select with cmake

doc/Doxyfile.in

@@ -91,7 +91,7 @@ ALLOW_UNICODE_NAMES    = NO
 # Ukrainian and Vietnamese.
 # The default value is: English.
 
-OUTPUT_LANGUAGE        = English
+OUTPUT_LANGUAGE        = ${DOXY_OUTPUT_LANGUAGE}
 
 # The OUTPUT_TEXT_DIRECTION tag is used to specify the direction in which all
 # documentation generated by doxygen is written. Doxygen will use this
@@ -1156,7 +1156,7 @@ GENERATE_HTML          = YES
 # The default directory is: html.
 # This tag requires that the tag GENERATE_HTML is set to YES.
 
-HTML_OUTPUT            = html
+HTML_OUTPUT            = html/${DOXY_OUTPUT_DIR}
 
 # The HTML_FILE_EXTENSION tag can be used to specify the file extension for each
 # generated HTML page (for example: .htm, .php, .asp).
@@ -1420,7 +1420,7 @@ GENERATE_QHP           = YES
 # the HTML output folder.
 # This tag requires that the tag GENERATE_QHP is set to YES.
 
-QCH_FILE               = pip.qch
+QCH_FILE               = pip_${DOXY_OUTPUT_DIR}.qch
 
 # The QHP_NAMESPACE tag specifies the namespace to use when generating Qt Help
 # Project output. For more information please see Qt Help Project / Namespace
@@ -2209,7 +2209,7 @@ TAGFILES               =
 # tag file that is based on the input files it reads. See section "Linking to
 # external documentation" for more information about the usage of tag files.
 
-GENERATE_TAGFILE       = html/pip.cfg
+GENERATE_TAGFILE       = doc/html/${DOXY_OUTPUT_DIR}/pip_${DOXY_OUTPUT_DIR}.cfg
 
 # If the ALLEXTERNALS tag is set to YES, all external class will be listed in
 # the class index. If set to NO, only the inherited external classes will be