Description:
------------
Several places in the code test for GNUC >= 4 before #defining API strings

 #elif defined(__GNUC__) && __GNUC__ >= 4
 #      define CWD_API __attribute__ ((visibility("default")))
 #else
 #      define CWD_API
 #endif

This is all very well but some versions of gcc (eg the version in RHEL4, gcc 3.4.6) supports visibility attribute; this is made worse because the configure script actually tests whether visibility is supported by the compiler and (if so) adds the -fvisibility=hidden compile flag. This means that none of the API symbols are visible when built on those versions of gcc.

Suggest adding a GCC_HAS_VISIBILITY or similar flag that the configure script can set after its test and that can be used in place of the GNUC >= 4 test above.