Improve chunk source file support for cross-platform builds

[mcayland]

This series comes from an experimental branch to try and build 3DMMEx on other platforms and solves two main problems when attempting to build on Linux:

• Use forward slashes instead of backslashes in file paths
• Fix filename case to allow build on a case-sensitive filesystem

The most interesting part of this series is that it appears the backslashes are currently escaped incorrectly when filenames are embedded with the output chunk file, e.g.

Before:

00389630  73 74 75 64 69 6f 63 75  72 72 65 70 6f 73 69 74  |studiocurreposit|
00389640  69 2e 63 75 72 00 00 00  00 52 43 47 47 66 00 00  |i.cur....RCGGf..|
00389650  00 ec 00 00 00 06 5d 00  00 00 00 00 00 03 03 15  |......].........|
00389660  73 74 75 64 69 6f 63 75  72 73 71 75 61 73 68 73  |studiocursquashs|
00389670  74 2e 63 75 72 00 00 00  00 52 43 47 47 67 00 00  |t.cur....RCGGg..|
00389680  00 49 01 00 00 06 71 00  00 00 00 00 00 03 03 15  |.I....q.........|
00389690  73 74 75 64 69 6f 63 75  72 73 69 7a 65 76 65 6e  |studiocursizeven|
003896a0  6c 2e 63 75 72 00 00 00  00 52 43 47 47 68 00 00  |l.cur....RCGGh..| 

After:

00389630  00 a4 dc 01 00 ff ff ff  ff 14 00 00 00 52 43 47  |.............RCG|
00389640  47 65 00 00 00 80 00 00  00 06 6c 00 00 00 00 00  |Ge........l.....|
00389650  00 03 03 17 73 74 75 64  69 6f 2f 63 75 72 2f 72  |....studio/cur/r|
00389660  65 70 6f 73 69 74 69 2e  63 75 72 00 00 52 43 47  |epositi.cur..RCG|
00389670  47 66 00 00 00 ec 00 00  00 06 5d 00 00 00 00 00  |Gf........].....|
00389680  00 03 03 17 73 74 75 64  69 6f 2f 63 75 72 2f 73  |....studio/cur/s|
00389690  71 75 61 73 68 73 74 2e  63 75 72 00 00 52 43 47  |quashst.cur..RCG|
003896a0  47 67 00 00 00 49 01 00  00 06 71 00 00 00 00 00  |Gg...I....q.....|
003896b0  00 03 03 17 73 74 75 64  69 6f 2f 63 75 72 2f 73  |....studio/cur/s|
003896c0  69 7a 65 76 65 6e 6c 2e  63 75 72 00 00 52 43 47  |izevenl.cur..RCG|

[benstone]

Thanks!