wineps.drv: Write-strings warnings fix and declare function static

[Andrew Talbot]

Changelog:
    wineps.drv: Write-strings warnings fix and declare function static.

diff -urN a/dlls/wineps.drv/ps.c b/dlls/wineps.drv/ps.c
--- a/dlls/wineps.drv/ps.c	2006-05-23 17:05:53.000000000 +0100
+++ b/dlls/wineps.drv/ps.c	2006-08-15 20:19:34.000000000 +0100
@@ -231,8 +231,7 @@
 }
 
 
-INT PSDRV_WriteFeature(HANDLE16 hJob, char *feature, char *value,
-			 char *invocation)
+static INT PSDRV_WriteFeature(HANDLE16 hJob, LPCSTR feature, LPCSTR value, LPSTR invocation)
 {
 
     char *buf = HeapAlloc( PSDRV_Heap, 0, sizeof(psbeginfeature) +