cmDefinitions: Don't store parent lookups

When looking up scopes, it is faster to not store the lookup locally to
keep the maps smaller and avoid extra allocations and rebalancing.
cmDefinitions: Avoid a find-then-insert when setting variables

Searching the map is not necessary.
cmDefinitions: Use a hashmap for faster checks

The hash map is much faster at checking that the map won't have what
we're looking for so that we can just go to the parent scope instead.
CMake Nightly Date Stamp
Merge topic 'dev/static-regex'

1b003c1f cmTarget: Remove an unused variable
7492a7b8 regex: Search on strings where possible
3e7194a2 regex: Use static regexs where possible
Merge topic 'vs10-refactor'

1edaef39 VS: Factor MS-tool-specific vcxproj settings into helper
808f4b1f VS: Re-order logic to group MS-tool-specific options together
13e6d559 VS: Set some options directly instead of using flag map
8f4bdcc6 VS: Remove always-true condition on compile options block
eaa9f2f8 VS: Refactor internal generator factory logic
2b3e7b6f VS: Fix vcxproj specification of empty output file extension
39af06e7 VS: Fix vcxproj elements specifying binary output locations
ee329d54 VS: Refactor flag table lookup
Merge topic 'android-platform'

42f74df6 Add basic Android platform module
Merge topic 'no-parse-directory'

b1c113d9 cmake: Do not open directories as scripts (#14966)
Merge topic 'WriteCompilerDetectionHeader-compiler-versions'

ddec418a Features: Add compiler version support to WriteCompilerDetectionHeader.
b7029576 Project: Add configurable name for version computation macros.
78acaafe Project: Separate simulated compiler id from version detection.
567af1a5 WCDH: Issue a better message for version compatibility.
Merge branch 'master' into next
WCDH: Document the alignof and alignas wrapper macros.
Merge topic 'doc-WCDH-align-macros' into next

34f95bcf WCDH: Document the alignof and alignas wrapper macros.
Merge branch 'release'
Merge branch 'master' into next
ProcessorCount: Update for HPUX 11iv3
Merge topic 'hpux-ProcessorCount' into next

dbc0f63d ProcessorCount: Update for HPUX 11iv3
Merge topic 'dev/variable-lookup' into next

e17a69bc cmDefinitions: Use a hashmap for faster checks
3b21705d cmDefinitions: Avoid a find-then-insert when setting variables
5abfde6c cmDefinitions: Don't store parent lookups