Packages not found, X11R7.1 build terminates

[J. Hart]

 > I get the following error which terminates the build :
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 > checking for XPROTO... yes
 > checking for X11... configure: error: Package requirements (xextproto
 > xtrans xau xcmiscproto bigreqsproto) were not met:
 >
 > Package xextproto was not found in the pkg-config search path.
 > Perhaps you should add the directory containing `xextproto.pc'
 > to the PKG_CONFIG_PATH environment variable
 > No package 'xextproto' found
...
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Does the X11R7.1 src directory contain an incomplete release ?
Are there still some modules required from the X11R7.0 release to 
complete the requirements ?

With Thanks