build errors with MSVC 2005 Express.

 Another case of a variable initialized in a header:
c:\dev\mustang\hotspot\src\share\vm\opto\idealKit.hpp(97) : error C2258: illegal
pure syntax, must be '= 0'
c:\dev\mustang\hotspot\src\share\vm\opto\idealKit.hpp(97) : error C2252: 'first_
var' : pure specifier can only be specified for functions
c:\dev\mustang\hotspot\src\share\vm\opto\idealKit.cpp(150) : error C2065: 'first
_var' : undeclared identifier
library_call.cpp
c:\dev\mustang\hotspot\src\share\vm\opto\idealKit.hpp(97) : error C2258: illegal
pure syntax, must be '= 0'
c:\dev\mustang\hotspot\src\share\vm\opto\idealKit.hpp(97) : error C2252: 'first_
var' : pure specifier can only be specified for functions

...moved initialization into the constructor.