#32 Remove quotation marks in plConfig.h.in

[Tom Schoonjans]

Remove quotation marks for PLPLOT_VERSION_MAJOR, PLPLOT_VERSION_MINOR and PLPLOT_VERSION_PATCH in plConfig.h.in
This is necessary to ensure that they are useful for comparing these version numbers in preprocessor macros like:

#if PLPLOT_VERSION_MAJOR >= 5 && \
    PLPLOT_VERSION_MINOR >= 11
        #define PLCALLBACK plcallback
#else
        #define PLCALLBACK plstream
#endif

This patch ensures that the preceding code snippet compiles when using PLplot 5.11.0: right now it fails...

[Tom Schoonjans]

[Alan W. Irwin]

This is a no-brainer fix we should have done long ago. So thanks very much for spotting and fixing this issue! I have just pushed your fix to master and it will be part of the forthcoming 5.11.1 release.