build on cygwin

To build sather-1.2.3 on cygwin, where case is ignored in checking make 
targets, I had to make the following changes beyond the CPP & PLATFORMS 
suggested in the Makefile

diff -r sather-1.2.3/Makefile sather-1.2.3-cygwin/Makefile
107c107
< full: compiler
---
 > full: Mcompiler
128c128
< compiler: system bootcompiler
---
 > Mcompiler: Msystem bootcompiler
184c184
< bootcompiler: system
---
 > bootcompiler: Msystem
192c192
< system: common library platforms
---
 > Msystem: common Mlibrary platforms
201c201
< library:
---
 > Mlibrary:
227c227
< test:
---
 > tests:

diff -r sather-1.2.3/System/Platforms/win32/CONFIG 
sather-1.2.3-cygwin/System/Platforms/win32/CONFIG
2c2
< EXEC_SUFFIX:           ".exe"
---
 > EXEC_SUFFIX:           ".exe";

This change eliminates some repetitive warnings from the C compilations:

diff -r sather-1.2.3/System/Common/floatmath.h 
sather-1.2.3-cygwin/System/Common/floatmath.h
23a24
 > #if !defined(M_LN2)
24a26
 > #endif

- Andy Hooper