Map load: upper/lower case file name mismatch warning inconsistency

System: Win10 / NTFS

Examples:

• map file: .\E1L1.MAP

• cmd line: eduke32 -map E1L1.map

• log: Using level: "/E1L1.map".

• map file: .\E1L1.map

• cmd line: eduke32 -map E1L1.MAP

• log: warning: case mismatch: passed "E1L1.MAP", real "E1L1.map"

• log: Using level: "/E1L1.MAP".