Extend buffer for reading lines from /proc.

Apparently a line longer than 255 chars was spotted in the wild:
http://serverfault.com/questions/577939/linux-ps-htop-show-processes-running-for-hundreds-or-thousands-of-days-though-h#comment676098_577939

Process.h

@@ -158,6 +158,8 @@ typedef struct ProcessClass_ {
 #define ONE_DECIMAL_M (ONE_DECIMAL_K * ONE_DECIMAL_K)
 #define ONE_DECIMAL_G (ONE_DECIMAL_M * ONE_DECIMAL_K)
 
+extern char Process_pidFormat[20];
+
 void Process_setupColumnWidths();
 
 void Process_humanNumber(RichString* str, unsigned long number, bool coloring);