compiling grass5.0beta7 on linux

[Eric G . Miller]

INFINITY is an ISO C 9x thingy. glibc 2.1 and gcc2.95 are ISO C 9x
ready, the older ones aren't (apparently). Here it's nested in

#if __USE_ISOC9X

enum {
   ...,
   FP_INFINITE,
# define FP_INFINITE FP_INFINITE
   ...
   };

/* Lot's of macros */
  ...
#endif
   
glibc2.1

The ISO C standard just went through end of last year.  So, pretty
recent C libs and compiler are necessary.