Parse M33 + GCC_ARM map files

[theotherjimmy]

Description

Turns out that under certain circumstances, GCC_ARM will emit
whitespace-delimited text in map files. Before this PR, Memap's
GCC_ARM map file parsing logic assumes that sections assumes
that the sections always start the string. This PR allows the
sections to be prefixed by whitespace.

Fixes #10109

Note for reviewers: the first commit cleans up lint warnings and
the second commit fixes the bug.

Pull request type

[x] Fix
[ ] Refactor
[ ] Target update
[ ] Functionality change
[ ] Docs update
[ ] Test update
[ ] Breaking change

[ciarmcom]

@theotherjimmy, thank you for your changes.
@ARMmbed/mbed-os-tools @ARMmbed/mbed-os-maintainers please review.

[bridadan]

Changes look fine, but you get to make travis happy now :)

[cmonr]

CI started

[mbed-ci]

Test run: SUCCESS

Summary: 11 of 11 test jobs passed
Build number : 1
Build artifacts