'Present but cannot be compiled' errors

[Ed Avis]

When building valgrind-2.0.0 I saw

configure: WARNING: fcntl.h: present but cannot be compiled 
configure: WARNING: fcntl.h: check for missing prerequisite headers? 
configure: WARNING: fcntl.h: proceeding with the preprocessor's result 
configure: WARNING:     ## ------------------------------------ ## 
configure: WARNING:     ## Report this to address@hidden ## 
configure: WARNING:     ## ------------------------------------ ## 

and the same for many other headers.  The gzipped config.log is
attached.

-- 
Ed Avis <address@hidden>

config.log.gz
Description: config.log from valgrind-2.0.0 with 'present but cannot be compiled'