WMS: Fix portability issues in WMS driver

[pvachon]

The attached patch fixes several issues in the WMS driver:

• the redeclaration of int i within the same scope in for loops (issue on MIPSpro and MSVC++)
• the usage of signed 1-bit bitfields (int m_something : 1) (issue on MIPSpro, and really is incorrect)
• the round() function is a C99 function. With a compiler that is strict about adhering to "standards," C99 functions are not available when building C++ code. This was replaced with floor(x + 0.5)

[pvachon]

The patch for the WMS driver. To apply, copy to the frmts/wms/ directory and run patch -p1 < wms_fixes.patch

[warmerdam]

Patch applied ... thanks Phil.